my vote is: tremolo sounds better after the preamp, the extra cables from the effects loop can be tidied up by making your own snake... what i did was i bought several guitar leads and an extension cord (to power my pedal board) and used heat shrink and gaffer tape to build my own snake to go from my amp to my pedal board. works like a charm, tidy, means i can use my effects loop without tripping over a bajillion cables. and i'm a student so DIY=cheap=gooooood
depending on your budget, yes boss are amazing but if you're poor like me the cheapy Nobels does the trick... can select multiple waveforms like the boss, sounds fine. but boss is better if you can afford it.