7Pyrhus wrote: Slap the thing that increases range, whatever it's called on the defriender and it'll pretty much become a sniper as well.
That is true, but the spread of the Defriender's shots mean that it becomes useless at long range even with the thing that increases range. This is because the farther the bullets go, the more spread out they are and therefore the smaller the chance that all bullets hit (because all of the bullets need to hit in order for maximum chances of a one-hit kill). Rehab, however, has all that damage concentrated on a single bullet and with deadly accuracy.
I think they're all pretty good weapons and it really depends on your playstyle.