I have the most experience in three bottom end guns: Trracers, Pirannahs,
and Stingrays.  Here's the run-down:

name            Trracer         Pirannah LB     Stingray
category        pump autotrig   pump            semi
cost            low             medium to high  very low
durability      low             high            medium to low
weight          very light      very heavy      medium
accuracy        high            high            medium to low
to de-splooge   mostly squeegee just shoot      must have a squeegee
expandable      very            very little     barrel   
maintenance     low             low             low to high
takeapart       with fingers    near impossible fairly easy
reliability     very good       very good       medium
cold-weather    lower velocity  doesn't care    cycles now and then
necessary mods  vel adj bolt    none            trigger job
best addition   14" Tru-Flight  veladj & AuTrig 20oz tank
sound           very loud       rather quiet    medium to loud
vel adjust      disassemble     remove bottle   hex wrench on outside
size            medium          small           large
rate of fire    fast            medium to fast  medium

I have owned all three.  The Trracer is my "main gun", to which I have
added 140 rnd Sight Feeder, 14" rifled barrel w/muzzle brake, velocity
adjusting bolt, 7 oz tank, and a scope.  I've since sold the Stingray
and Pirannah. (should've kept the pirannah as a backup though...)

bottom line:

Trracer: fragile design, but very good performance and use.  Treat the
         gun with care, and it will deliver the goods.
Pirannah: closed system, hard to upgrade or maintain.  It has many good
          points, but you're committed to its good/bad points.
Stingray: low cost, low quality, some nice extras.  A good deal if you
          want a semi and don't have much cash.  Quality is a gamble --
          some are good, some are bad, no telling which.  Good idea to
          own some tools and know how to fix things.