IMO, i had a BT-4... still got it today, and i love it... only one person i know has sold theirs after owning it a year or 2! but electric markers are better
also depends what ure using it for... i mainly kept my bt-4 so that when my mates go for "experience days" paintballing... i have a gun that doesnt jam/misfire/use as much air/wildly innaccurate as the rent-a-guns!
as YT 69 said it all depends on the type of paintball your wanting to play,
. sup'air= electric eg ion/pmr (cheap)
. wood= mech or electric eg infreno/ion
. or walk ons which is pretty much the same as woods, mech or electric.