Interesting question. First I wouldn't pick any of those and rather would make a gun to my specs. But if I could only have a gun from those you listed my reasoning would be as follows.
I like to hip load so that right away disqualifies everything but the Riffes because competitor series also comes with butt extension. Of the two I would go with the competitor series because it's lighter and is perfectly capable of handling two 5/8" bands and a 7mm shaft which is all I need for fish up to 50lb. If I was consistently going for bigger fish I would consider the standard series with a 5/16" shaft and two 5/8" bands plus one 9/16" bands.
Of course the first thing I'd do is get rid of the safety and the handle and put a custom handle on the gun.
That will make the gun usable for me but not ideal. I prefer a length between the C3 and C4 with two holes rather than a band slot which will give me a couple of more inches of band stretch. I also prefer a shaft with a single tab closer to the mech which gives me another inch of band stretch.
IF I could chest load I would go with an Aimrite because it has a steel trigger mechanism. See my post on the RA trigger mech, I couldn't believe it when I saw it. The only thing I would do to the Aimrite is get rid of the safety.
I'm not too concerned about accuracy. If the gun has a solid trigger mech that won't fail and it's not overpowered any one of those should shoot straight.