There's a reason GM doesn't make just one car...I have never shot, held or owned a zipper bow, but have owned and shot everything else on the market.
There are a lot of great bows on the market and when it comes down to a comparison to two great bows and which one is better? Well, I believe it all comes down to splitting hairs and personal preferences. There is always those subtle differences that is either positive or negative to each individual archer.
If it means anything I think the TT's is the best all around bow I have ever shot, and my Father n law who is a huge Bear fan, who's been shooting the same bear takedown for 40 yrs with everything from moose, elk, caribou, deer and bear with this same bow who is so tight he squeaks, shot my tall tines and is truly impressed with this bow and shoots it better than his bear take down.
I would also look at the customer service side which is everything to me...Guarantee you there is one or two great bows out there but because of the personality deficiency of the Bowyer I would never own one of their bows.
Don't know the people of the Zipper bows, sounds like they are great people...never knew Brian Wessel before I purchased a Tall Tine, but I do call him my Friend today.
Good Luck on your search my Friend.
George