Demo them both if you can. I personnally prefer the Kendos and feel that they are a great all-mountain ski. The Kendos really surprised me with how well they held an edge and carved through the gnarliest of refrozen crud with their lighter weight. These skis did not get deflected or shoved around at all. They ripped both big soft bumps and smaller hard ones as well as 18" fresh powder and the later in the day tracked up snow. Last but not least they held an edge on the ice as well.
All of this in three days of skiing at Blackcomb on Dec. 12, 13and 14th last month. Caught the tail end of a Pineapple Express the first day, transition temps/conditions day two and awoke to an unexpected fresh dump for day three. I found the Kendos outstanding in all of the conditions.
Even with their longer turning radius I found the Kendos to be quicker under foot and very agreeable to shorter radius turns. They were very stable and solid at speed with GS turns on the hard(snow) groomers giving up nothing to the AC50s. I skied the AC50s last season at W/B in a 177 and the Kendos in a 184. I found the AC50s very solid under foot, great grippers and hardpack rippers as well as solid in the crud but for me weren't as snappy/quick. I skied the AC50s in very harsh, icy and frozen/wind swept conditions very similar to several runs on the Kendos and give the nod to the Kendos because of their quickness and non plank-like feeling. The Kendo is a ski I would be happy skiing all day long at my local areas as well as the big mountain resorts in any terrain. The AC50 for me would be a bigger area, front side ski that I could ski all day on the groomers, which I don't, but would become tiresome in the couloirs.
For me the Kendo would be the way to go. I'm waiting for the right deal to come along....Phil?...anybody?
Just for reference I'm 5'11", 170ish and a solid, all mountain skier.
Hope this helps and I apologize if it's too Blah, Blah Blah :)