Cool, welcome (soon) to the club of dual drives
Right now I have only a rear, however, until a few days ago was riding with only a front with a day of dual drive in the middle

Here are my thoughts on the matter:
-I like front a lot better for powering into turn and also for slippery weather. I guess this is only because with a front and me pedaling I have effective 2wd even with only one motor. The front will slide around and spin out but usually its is still pulling forward which keeps you upright. I noticed this both on trails and on slippy roads.
-With a rear hub it just feels more natural... I like the push feeling of the motor vs the pull of a front hub
-As you already stated when going up a hill the rear hub does much better... a front hub will start to spin if you don't help it along and it gets steep enough / loose enough
-Front hub feels more stable at higher speeds... when I had an extra 15 pounds in the front that low to the ground the bike handled better at higher speeds.