IMO the maxus is a clear shot winner when compared to these two
The SBE2 is now old technology. The way the new Vincis are operated will probably be the standard before all that long.
The spring is directly behind the bolt and not in the stock which reduces muzzle flip. It's a great design.
As to why people shoot 3.5s, it's all I shoot. I shoot them because I can and because I sometimes hunt in fields where I may have a longer shot and I want the heavier payload and more powder to be able to knock down and not cripple a bird.
Besides, I'm already spending a fortune to be able to hunt why would I worry about another $40 or so on a case of shells?