Hi Skeb The Allstar is a great Board. I am 88kg and 6'3 and have the 14' x 26". It is great on the flat, but you notice the reduced volume and width on the ocean with a higher centre of gravity - oh if we all had Danny Ching's short legs!
I'd recommend the 27" wide for the bigger/taller guys. Still much lighter than the 2012 Coast runner and great new shape for 2013.
What size 12'6 or 14' ? At merimbula i did the 2 races on the 12'6X26 Allstar floated my 100kg's fine last weekend did the Queenscliff race in Sydney on the 14'x27.5 Allstar. Felt great in the tuff conditions. If your riding the 27 Ace already than the 26 should be fine. I have a friend with the 14'x26 but haven't ridden it yet to compare. as for speed difference can't really help.