So I got my Toko order last week and broke out my new T14 two nights ago.
The base plate specs suggest that the T14 base plate isn't any bigger than that on the T77, but it sure waxes like it is. I don't know if it's a difference in element setup or what, but on a moderately wide ski (130/100/121), the T14 can do the whole width of the ski in one pass. With the T77, I found that the edges don't heat sufficiently on similarly sized skis and I need to make multiple passes.
On a really wide ski (142/120/135), the iron appears wide enough, but I can't get the whole base to heat up at once. I'm guessing that's a base-flatness issue, though, and not an iron issue, and I'm not going to try to fight a 120mm-waisted ski into a flat base.
The temperature is more consistent; with the T77, I fairly often end up needing to tweak the dial during waxing and then put down the iron and let it stop smoking. Over 2.5 pairs of skis, the iron maintained a consistent temperature and never got overheated or cooled enough to be a problem. (2.5 pair = two adult pair and a 70cm pair)
It's not a night-and-day difference, but it's definitely a noticeable improvement. With a new baby in the house, saving the three or four minutes that I usually spend dinking around with the temperature dial per pair of skis will add up, and not having the iron suddenly start smoking is much-appreciated.