They are very close in performance, some reviews indicate that the 1100T is a slightly better overclocker. The price difference in the U.S. is only $10, not sure there's 30 euros worth of difference though.
What Mizzou said.
I just replaced the 1055T with a 1100T while I wait...and wait...and wait for the !#&*%!#@ Bulldozer to come out...but I digress, I thought I might be able to get a bit more OC out of it as it's binned at the top of the series. I did get an extra 150Mhz from it and at a bit less voltage, but that is never guaranteed, so you have to decide if the extra 30 euros is worth it to you.
not much. I would not go more than 3.6-3.7 ( the turbo boost) if you get either, I would figure an aftermarket cooler into the budget.for OC'ing. The stock cooler is a basic square aluminum fin array with a single heatpipe.
I am running my 1100T @ 4.3Ghz ( a reasonable expectation) but you will not get anywhere near that with the retail cooler.
If I was to use the stock cooler, by how much could I overclock with both processors?