I bought the MPA over the other because of the spring assist, Specter says using buffer tube with spring will more likely attract attention of RCMP then their design, I think using and AR-15 Bolt carrier would attract more, other rifles use the buffer tube design for adjustable butt stock, but I can't think of another rifle that usses a AR-15 Bolt carrier other than an AR-15. I like the idea of spring assist, I think it would be faster and less work to cycle action. Troy straight pull rifle has the same design with spring assist. MPA uses it own Bolt carrier design and stated it could never be converted to semi
Having to pull the buffer tube off to get at the bolt is a pain, like the JR Carbine, but with no gas getting needing to cycle action, how dirty can it get, so you probably would only need to take it apart once a year