I have only used the big full size M249 SAW and hated it. I saw the the Ultimax in Singapore and it looked awesome how the guys could move around with it because it was so light weight. I have only read about it's A+ reviews, but never got to shoot or handle it.
I went with the Stoner 63 LMG/commando. The Stoner just looks sexy and I always have had a hard-on for it ever since I was a kid after reading The Element of Surprise.