Southpaw here.
Shoot both and it will be obvious as to which one you will want to keep, provided you shoot left handed.
It seems that your looking to simply "target shoot", and since no mention of formal competition was mentioned, I would suggest that you shoot both, and find out as to which is "the most accurate" for you and the way you plan to shoot (Ie... shooting positions)
Are you asking for an accuracy comparison between a Springfield Armory Inc. M1A Supermatch vs a rack grade M1 Garand? I'll give you a hint. Take both next to each other and look at both rear sight apertures. Is the one on the SM hooded, while the M1 is not? Any differences in both concerning size of the aperture holes themselves? any bbl markings that you can see on the M1A's tube?
(Just the tip of the iceberg here.)
Request:
Please post pics of both rifles, as this will help others see what you actually are looking at now.
FWIW, I would not sell either to fund a bolt gun, regardless.
Reasons:
True M1 Garands will eventually dry up, and the folks who bought them CMP rack grade Garands will see this investment skyrocket. If you really want a custom built bolt gun by then, your M1 might just sell for enough to cover the bolt gun and the optics to go with it. ( I sold mine and regret it, but not enough to replace it on account of my addiction to the M1A/M14)
M1A rifles of any model are not going to get any cheaper in the future either. You have one of the most southpaw friendly rifles out there. Enjoy it.
Last but not least, when you can honestly tell yourself that you can shoot both rifles to their full potential, then it might be worth it for you to sell one to fund a precision bolt gun at that time.
11B