I've ordered off both. I found maximumrobotics to be nice friendly people who answered my emails quickly and order things in that where out of stock for me.
Futurlec, where cheap cheap cheap. Took quite a while for shipping (to Ireland, maybe a month) and some parts where missing on arrival, but they sent them out when I emailed them. So not a horror story, but I've read about people having trouble with them.
Its a matter of quick delivery and peace of mind against cost.