i prefer working on rear wire myself. i find front to be slightly finicky to work. mainly if you try to use heavy awg or silicon insulated wiring.
the delicate ribbon cable of an ASCU is also more at risk in a front setup.
most important of all is m4 m16 takedown, as mentioned above, is easy with rear wiring.
that said, front wiring is very flexible regarding stock and battery placement. i have lipos that are two ounces. if you dont like a front heavy gun you can put one of these up front and preserve balance.