I’ll give you my 2 cents impression, as I have owned or own all of these rifles.
Started with the MRAD. Good gun, decent trigger, built like a rock, and good factory barrel accuracy. Barrel and bolt swaps were the weakest of the 3 mentioned but still just a few minutes total for short to long action conversions. Very poor availability of any aftermarket barrels, I don’t know of any actually. Easily 1/2 or less MOA with handloads in all 3 caliber I owned, 6.5 Creedmoor/308/338 Lapua.
Desert Tech SRS, average single stage trigger, very comfy, and easily the best barrel and bolt swap system. Under 90 seconds to go from short action to long action. Best repeatability in barrel poi. Very rarely more then 1/4 moa difference. Tons of aftermarket barrels and calibers. I have the standard, magnum and long action bolts and you can order any caliber under the sun, as long as it fits the bolt heads. Insite Arms has made me more then 10 barrels for mine and have used Kriegers/Bartliens/Benchmark barrels in my SRS and it hammers with everything. Just quick hand load work up and that chassis is just a rock. The biggest factor in accuracy between this chassis and any other, to me, comes down to your gunsmith and their magic. Can’t beat Insite in my opinion. Harley is gold in over 15 barrels so far. Ask anybody who gets one of his barrels. The mag system is not smooth but does work ok, and the mags Do have huge coal for long handloaded stuff. It’s a unique piece and fit, but I absolutely love it!
I also own an AI AT, with 2, and soon to be 3, Insite barrels. Best factory precision sniper rifle on the planet in a standard configuration, inmo. Stock trigger can be tuned quite good, and aftermarket triggers now coming available. Great barrel swap system too, but you are confined to just one bolt head size. So no long and short action swapping. Great factory and aftermarket mags. Super accurate, same as the SRS, but better trigger. Tons of aftermarket barrel options. Insite makes profits for these too.
I also own a full custom MPA chassis build from Insite, with a short action Surgeon 591 action and 4 barrels. Harley made it a switch barrel system as well. Run Bix n Andy Comp trigger, and it is the best trigger of all my rigs. With a custom you don’t save any money over the high end factory stuff, but you get exactly what you want.
All the barrels cost the same.
I sold my Berrett because they only make right handed rifles, and I’m a leftie, but it would still be my last choice between these. Great rifle though and not dissing it. Least flexible system and caliber options. Mags were smooth as glass though.
The other 3 systems are all tied, lol, like them all equally. Honestly can’t go wrong with any of them. All will shoot tiny groups with good ammo and good barrels.
The AI and SRS are heavier chassis systems though, if that’s a consideration.
