First bike specific shoes

Nothing wrong with using MTB shoes in a tri...it's what I used for my first two races.  I loved the fact that I could actually jog in them without worrying about slipping.  And the bonus to getting MTB shoes, is that you can also use them in spinning classes (if you happen to do that).   In regards to the type of closure system on the shoes...I've always liked the velcro straps, because they're easily adjusted and quick to put on and take off.   My MTB shoes were from Specialized...but there are lots of other brands out there (Shimano, Louis Garneau, Sidi, etc.).  It's best to try a few different pairs on to see which fits you the best, as the fit/sizing can vary slightly between brands. 

Thanks for the input.  I am going to hit Tri sports in Hilton Head this weekend and see what they have.  With such a large foot its tough to get something in stock but I think your right about the MB shoes and I will feel better with a little traction.

I use MTB shoes and I like them.

I'm very similar in size - 6'3" and 205 w/ a size 13.  I got Lake MX85 MTB shoes, I spent around $80, the site has them listed for $70.  Not the cheapest, but not the most expensive either.  Which is good, because the more you spend on MTB shoes, the softer they become.  You'll want a stiff shoe to be more like a road shoe.  They do have 3 straps, but I have found I only need to loosen the top one to get in and out. 

I also find that MTB shoes are easier to 'scooter' start and stop (not sure if that is the propper term, but its when you have one foot one a pedal, and push off w/ the other foot and then fling your leg over)  You wont have to clip in b/c the tread will keep you in place (for the most part)
I can pretty much mount, ride and dismount w/o having to be clipped in.

And one more thng about MTB shoes.  If you want to stop during a ride and go into a store, you can w/o worry, some stores wont allow cycling shoes in b/c they mark up their hardwood floors.