If they had retired one year earlier: DiMaggio more Home Runs than Strike Outs; Mantle .302 Batting Average.

Joe DiMaggio retired after 1951. Mickey Mantle retired after 1968. Both retired after his age 36 season. Career Home Run leaders through 1950:

Rk	Player	HR	From	To	Age	G	PA	AB	R	H	1B	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	OPS+	TB	GIDP	HBP	SH	SF	IBB	Pos	Team
1	Babe Ruth	714	1914	1935	19-40	2503	10626	8399	2174	2873	1517	506	136	714	2214	123	117	2062	1330	.342	.474	.690	1.164	206	5793	2	43	113		34	*971H83	BOS,BSN,NYY
2	Jimmie Foxx	534	1925	1945	17-37	2317	9677	8134	1751	2646	1529	458	125	534	1922	87	76	1452	1311	.325	.428	.609	1.038	163	4956	69	13	71		133	*3H25719/6	BOS,CHC,PHA,PHI
3	Mel Ott	511	1926	1947	17-38	2730	11347	9456	1859	2876	1805	488	72	511	1860	89	90	1708	896	.304	.414	.533	.947	155	5041	82	64	109		128	*958H7	NYG
4	Lou Gehrig	493	1923	1939	20-36	2164	9665	8001	1888	2721	1531	534	163	493	1995	102	100	1508	790	.340	.447	.632	1.080	179	5060	2	45	106		102	*3H/976	NYY
5	Joe DiMaggio	349	1936	1950	21-35	1620	7190	6406	1318	2105	1262	367	127	349	1466	30	9	729	333	.329	.401	.589	.990	158	3773	114	40	14		108	*879H/3	NYY
6	Johnny Mize	341	1936	1950	23-37	1612	6731	5870	1066	1863	1099	341	82	341	1232	27	12	797	468	.317	.403	.578	.981	163	3391	85	44	20

Joe DiMaggio through 1950:
349 Home Runs
333 Strike Outs

And DiMaggio was fifth in career home runs, as he was still when he retired after 1951:

Rk	Player	HR	From	To	Age	G	PA	AB	R	H	1B	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	OPS+	TB	GIDP	HBP	SH	SF	IBB	Pos	Team
1	Babe Ruth	714	1914	1935	19-40	2503	10626	8399	2174	2873	1517	506	136	714	2214	123	117	2062	1330	.342	.474	.690	1.164	206	5793	2	43	113		34	*971H83	BOS,BSN,NYY
2	Jimmie Foxx	534	1925	1945	17-37	2317	9677	8134	1751	2646	1529	458	125	534	1922	87	76	1452	1311	.325	.428	.609	1.038	163	4956	69	13	71		133	*352H79/16	BOS,CHC,PHA,PHI
3	Mel Ott	511	1926	1947	17-38	2730	11347	9456	1859	2876	1805	488	72	511	1860	89	90	1708	896	.304	.414	.533	.947	155	5041	82	64	109		128	95H87/4	NYG
4	Lou Gehrig	493	1923	1939	20-36	2164	9665	8001	1888	2721	1531	534	163	493	1995	102	100	1508	790	.340	.447	.632	1.080	179	5060	2	45	106		102	*3H/976	NYY
5	Joe DiMaggio	361	1936	1951	21-36	1736	7672	6821	1390	2214	1333	389	131	361	1537	30	9	790	369	.325	.398	.579	.977	155	3948	130	46	14		111	*879H/3	NYY
6	Johnny Mize	351	1936	1951	23-38	1725	7104	6202	1103	1949	1160	355	83	351	1281	28	12	833	492	.314	.400	.568	.968	160	3523	92	48	20

Joe DiMaggio through 1951:
361 Home Runs
369 Strike Outs

Mickey Mantle's cumulative stats show that his career batting average (BA) peaked after 1957: .316 after Mantle had by far his two highest season BA:

1956: .353
1957: .365

Cumulative BA through:
1964: .309
1967: .302

1968 splits: highest monthly BA by far was .288 in Sep/Oct. He had to rally in his final month to get up to .298. July: .198.

According to Vince Gennaro:

I did a little research. Mantle's career batting avg dipped below the official .300 level (which means below .2995) for the first time, never to return above that line on July 12th 1968, in the top of the 8th inning at Comiskey Park, when he grounded out against Wilbur Wood. (Note: earlier in the season, on May 30, 1968 Mickey went 5 for 5 with 2 HRs vs. the Senators)

_____________________________

Career Home Run leaders through 1967:

Rk	Player	HR	From	To	Age	G	PA	AB	R	H	1B	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	OPS+	TB	GIDP	HBP	SH	SF	IBB	Pos	Team
1	Babe Ruth	714	1914	1935	19-40	2503	10626	8399	2174	2873	1517	506	136	714	2214	123	117	2062	1330	.342	.474	.690	1.164	206	5793	2	43	113		34	*971H83	BOS,BSN,NYY
2	Willie Mays	564	1951	1967	20-36	2298	9814	8632	1679	2668	1554	426	124	564	1575	287	87	1070	1066	.309	.384	.583	.968	160	5034	199	31	7	70	180	*8H/96735	NYG,SFG
3	Jimmie Foxx	534	1925	1945	17-37	2317	9677	8134	1751	2646	1529	458	125	534	1922	87	76	1452	1311	.325	.428	.609	1.038	163	4956	69	13	71		133	*352H79/16	BOS,CHC,PHA,PHI
4	Ted Williams	521	1939	1960	20-41	2292	9792	7706	1798	2654	1537	525	71	521	1839	24	17	2021	709	.344	.482	.634	1.116	191	4884	197	39	5	20	258	*79H/1	BOS
5	Mickey Mantle	518	1951	1967	19-35	2257	9363	7667	1619	2312	1393	330	71	518	1455	147	36	1627	1613	.302	.423	.566	.988	173	4338	104	12	13	43	141	*8937H/645	NYY
6	Mel Ott	511	1926	1947	17-38	2730	11347	9456	1859	2876	1805	488	72	511	1860	89	90	1708	896	.304	.414	.533	.947	155	5041	82	64	109		128	95H87/4	NYG
7	Eddie Mathews	509	1952	1967	20-35	2360	10044	8485	1505	2304	1369	354	72	509	1445	68	39	1439	1475	.272	.377	.510	.887	144	4329	123	26	36	58	141	*53H7	ATL,BSN,DET,HOU,MLN
8	Lou Gehrig	493	1923	1939	20-36	2164	9665	8001	1888	2721	1531	534	163	493	1995	102	100	1508	790	.340	.447	.632	1.080	179	5060	2	45	106		102	*3H/976	NYY
9	Henry Aaron	481	1954	1967	20-33	2119	9212	8283	1519	2618	1602	451	84	481	1541	187	54	802	929	.316	.374	.565	.939	157	4680	218	22	19	86	177	*9874H/53	ATL,MLN
10	Stan Musial	475	1941	1963	20-42	3026	12721	10972	1949	3630	2253	725	177	475	1951	78	71	1599	696	.331	.417	.559	.976	159	6134	243	53	35

In 1968 Mantle would pass both Williams and Foxx to finish third in career home runs. But Mantle had already hit number 500:

Sunday, May 14, 1967

Attendance: 18,872

Venue: Yankee Stadium I

Game Duration: 2:38

Day Game, on grass

Yankees 6, Orioles 5

HR: Joe Pepitone (1, off Stu Miller, 6th inn, 1 on, 2 outs to RF); Mickey Mantle (4, off Stu Miller, 7th inn, 0 on, 2 outs to RF).

Career Home Run leaders through 1968:

Rk	Player	HR	From	To	Age	G	PA	AB	R	H	1B	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	OPS+	TB	GIDP	HBP	SH	SF	IBB	Pos	Team
1	Babe Ruth	714	1914	1935	19-40	2503	10626	8399	2174	2873	1517	506	136	714	2214	123	117	2062	1330	.342	.474	.690	1.164	206	5793	2	43	113		34	*971H83	BOS,BSN,NYY
2	Willie Mays	587	1951	1968	20-37	2446	10387	9130	1763	2812	1650	446	129	587	1654	299	93	1137	1147	.308	.384	.578	.962	160	5277	212	33	7	76	187	*8H9/3675	NYG,SFG
3	Mickey Mantle	536	1951	1968	19-36	2401	9910	8102	1676	2415	1463	344	72	536	1509	153	38	1733	1710	.298	.421	.557	.977	172	4511	113	13	14	47	148	*8397H/645	NYY
4	Jimmie Foxx	534	1925	1945	17-37	2317	9677	8134	1751	2646	1529	458	125	534	1922	87	76	1452	1311	.325	.428	.609	1.038	163	4956	69	13	71		133	352H79/16	BOS,CHC,PHA,PHI
5	Ted Williams	521	1939	1960	20-41	2292	9792	7706	1798	2654	1537	525	71	521	1839	24	17	2021	709	.344	.482	.634	1.116	191	4884	197	39	5	20	258	*79H/1	BOS
6	Eddie Mathews	512	1952	1968	20-36	2391	10101	8537	1509	2315	1377	354	72	512	1453	68	39	1444	1487	.271	.376	.509	.885	143	4349	123	26	36	58	142	*53H7	ATL,BSN,DET,HOU,MLN
7	Mel Ott	511	1926	1947	17-38	2730	11347	9456	1859	2876	1805	488	72	511	1860	89	90	1708	896	.304	.414	.533	.947	155	5041	82	64	109		128	*958H7	NYG
8	Henry Aaron	510	1954	1968	20-34	2279	9888	8889	1603	2792	1710	484	88	510	1627	215	59	866	991	.314	.373	.560	.933	157	4982	239	23	19	91	200	*9874H3/5	ATL,MLN
9	Lou Gehrig	493	1923	1939	20-36	2164	9665	8001	1888	2721	1531	534	163	493	1995	102	100	1508	790	.340	.447	.632	1.080	179	5060	2	45	106		102	*3H/976	NYY
10	Stan Musial	475	1941	1963	20-42	3026	12721	10972	1949	3630	2253	725	177	475	1951	78	71	1599	696	.331	.417	.559	.976	159

Mays drew closer to 600 and Aaron reached 500. Mantle and Mathews retired after 1968.