I've got an HRA Correct Grade M1 as well as a Springfield Special Grade M1 (completely refurbished rifle consisting of an original M1 Garand Springfield receiver, new production Criterion barrel, new production American Walnut stock and handguards, and new web sling). In addition, I've also got a Springfield M1A with walnut stock to which I added a NM rear aperture (came with a NM front sight). In effect, the Springfield Special Grade M1 was NIB as was my and Springfield M1A and both now have over 1,000rds through them.
My son and I shoot the Springfields (as the HRA is too fine a condition to shoot), he the M1 mostly and me the M1A mostly. Both are excellent rifles, accurate and great to shoot. I lean towards the M1A because the M14 was my basic training rifle and I maintained an arms room full of M14s for a year so I have history with it. I like the heft and how well it shoulders and the 20rd mag capacity better, however, the M1 is also fine with me; slightly trimmer but the feel is the same as the M1A. I handload for both of them and the cost of the ammo is virtually identical as I use the same W748 powder, 147grn FMJ Bullets, and same WLR primers in each so no advantage to either. As both shoot the same bullet at the same velocity,performance is pretty much identical so they perform the same too. Both are a joy to shoot and get a lot of looks from the plastic and aluminum crowd at the range.
Now as to the AR10. While I have 2 ARs, a RRA mid length carbine and RRA 20" scoped A4, I'm just not fan of the bulky receiver and the plastic, fantastic feel of them. Yes, they are accurate but not fun to shoot. To me they just don't feel like a real rifle. I've shot friend's AR10s numerous times when we traded so they could shoot my M1A (they always want to shoot my M1A while I'm not interested in their AR10s) and in truth, the AR10 to me is just a worse version of the AR15; bigger, bulkier, and still plastic fantastic. Everyone who I let shoot my M1A really likes it and a couple have gone on to buy an M1A to go with their AR10.
My M1A feels head and shoulders better in use and as an 'irons only' comparison between the two, I'm a better shot at 300yds on bowling pins using my M1A and NM sights than any of the 'irons only' AR10s I've tried. I've also shot steel plates at 400yds with my M1A as well as a scoped M1A and scoped AR10. I still prefer my irons only M1A over either the scoped M1A or scoped AR10, however, if the OP plans to add a scope to his choice, I'd give the nod to the AR10 as the ergonomics of it with the scope is better than the M1A to me. That said, the bulk of both scoped rifles doesn't do it for me as I really like the lean feel of the M1A with irons.
So, to answer the poll, if we're talking an 'irons only' platform, I'd pick the M1A hands down, however, if we're talking a scoped rifle, the AR10 wins in my book by a slight margin.