I was in a similar situation and was looking into any switchbarrel system. I ended up checking out everyone I could find at shot show this year. While I have only been able to shoot the AI I did try to wear out one of each at the show. I did end up with an AI AXMC in the end from mile high. however opinions are like you know what and everyone has one. Here's mine
MRAD
Ergonomics – I actually like the MRAD a lot more than I thought I would. Everything seemed to be well placed and comfortable. Barrel swaps were pretty straight forward and easily done in the field.
Price – price was probably the best of the switch barrel systems. The barrel conversions were a decent bit more than some of the others so I think it would even out on the system price in the long run.
new calibers – unfortunately you can only get new cals from Beretta from what I understand. They do have a decent offering that is expanding from the looks of it. I asked the rep what the chances were of buying a caliber of your choice if they didn’t have it and his response if enough people wanted it they would make a run of them. I took that to mean probably not going to happen until it was a pretty popular caliber.
SRS A1
Ergonomics – Like others said this is hit or miss. I didn’t mind the bull pup too much but couldn’t get beyond the trigger and possible weak side shooting. Trigger is very good for a bullpup but still suffers from being a bullpup. Loved the overall size though and it would be super handy to get around. Absolutely did not like the magazines though.
Price – pretty close in price to the mrad I think. Barrel conversions are still a decent bit I think a little more than the mrads.
new calibers – decent offering from the factory and they also offer a “kit” that you can buy the barrel “bushing?” not sure what its called but includes a print that you can have a smith turn a barrel in whatever you want.
AXMC
Ergonomics – like the rifle a lot. Very heavy though esp with my saker can on it. Honestly my 2 stage trigger is not quite as good as I would like there is a slight amount of creep in it and may talk to AI about it soon. Barrel swaps are pretty easy and straight forward.
Price – pretty damn expensive up front. Every freaking thing is expensive (I think an extractor is like $100 alone). You can get barrels cheaper than the rest though usually around 650-850 for stainless bartleins.
new calibers – nice thing is you can get just about anyone to chamber whatever you’d like since there are no special parts. if you get the short action its even better since the blanks are more readily available. Although you lose the magnum capability you would gain a small firing pin from the factory. It was a pretty hard toss up for me to decide between these 2 to be honest.