I asked the guys at DeWALT this week.
The answer was a little surprising. The only difference between the two models is the D27105 has a slightly higher power output (1700 watts compared to 1400).
All other features such as cutting capacities are exactly the same.
Again, its down to personal choice about power. I guess that you will know if you want a lower powered saw. I just know that for the sometimes difficult site work I do, I need every watt!