The extra 20mm will slacken the headtube angle by about 1 degree and raise the front and bottom bracket a bit. So that could alter the way the bike handles. Whether thats bad or good...it up to you.
What I am noticing is that "XC" bikes are going more travel. Some 100mm bikes are being offered with 120mm forks now. Niner used to have their EMD 9 geometries with a 80 and 100mm fork. Now they dropped the 80 and replaced it with a 120mm fork geo. Far as I know...the EMD frame did not change.
Pivot also came out with their slightly longer travel Mach 429. From 100 to 116mm.
If you want a more "Trail" style ride...then I would try the 120mm. If I get a new fork...that is probably what I will go with.