top feed = smaller amount of paint and more of a finer detail gun as a lot of them usually come with a finer needles. You can buy finer needles for the bottom feeds too.
You can use color cups on your bottom feed to get pretty much same results as a top feed. I use the Badger color cups they will fit the Iwata. That way you buy one gun and use it both ways.
Badger color cups - Google Product Search
The bottom feed will probably not come with a very small dia. needle but I find it to be pretty much good enough for plugs. Everyone has their favs. like asking who likes Chevys who likes Fords.
BTW I have the HP-BCS and find it plenty good enough for anything I do. I also have a Peak top feed also and usually only use it for doing my stencils with black, still a good deal and a nice brush. Bear Air is where you will find them.
http://www.bearair.com/
I got the Iwata and most of my stuff at Dixie Art
http://www.dixieart.com/ but have not bought much of anything from either in a good 2 years so I am not sure they are the best deals around anymore.
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