Ultegra and 105 front shifting (as far as brifter action) will have no noticeable differences. Both are made to work with doubles or triples. The trim is only in the small ring (1/2 shift keeps you from cross-chaining when you are in the small ring/small cog combo). Dura Ace is double or triple specific (though I'm not sure that 7900 series has a triple option yet). However, DA7801 (for doubles) does have front derailleur trim when you are in both rings (there's a 1/2 shift either direction).

Many people seem to have a hard time with the harder, longer throw of the large lever for 105/Ultegra shifters (DA is an easier hand motion). So, people are maybe more likely to mis-shift and wind up trimming the FD by accident.