I cut my tanking teeth on the M60 series, first as an M728 CEV crewman and later as a platoon leader of an M60A3TTS platoon. I've got almost every M60 kit on the market, although I've never heard of the Royal Models one. Is it a detail set?
The old Esci M60A1, M60A3TTS, M60A1 Blazer was the best overall 60-series tank kit. Currently, Italeri reissued the M60A1 and Blazer and Revell of Germany has reissued the M60A3. Same Esci/Ertl/AMT kit inside though.
When did you serve on USMC M60A1s? The problem in using the ex-Esci kits is that none of them will build into a late 80s to early 90s USMC M60A1 RISE/Passive out of box. Problems arise in the areas of air cleaner type, barrel type and road wheel type. Then of course, if you rode a tank with the applique armor system, the Blazer kit is the Israeli type and not suitable for a USMC vehicle.
Tamiya and Academy both make a decent USMC M60A1 RISE/Passive tank, although the base M60 kit is not as accurate as the ex-Esci kits. The benefit is that you can build a good kit with what's in the box. The tracks are a little inaccurate and you can replace them with AFV Club T-142 tracks if you so desire. Tamiya also made an M60A3 kit that could be built into an earlier non-ERA USMC M60A1 but it still has the aluminum road wheels.
AVOID THE TRUMPETER M60A1 OR M60A3! I made the mistake of buying one of these. A total waste of money, it is a rip off of the Academy M60A1 but looks like someone left the kit under a heat lamp. Even uses a rip off copy of the Tamiya instructions. Funny thing is that they molded some of the detail parts onto the hull surface but the instructions still point out the part numbers and placement.