I upgraded my aeg for two reasons.
1) So I can shoot .25's like I do .2. This was done so I could shoot thru bushes and foilage easier and for better accuracy.
2) The extra range with .2 gives me a little advantage over people with stock guns. When they think they are out of range their not! I see there bb's coming and fall 15 feet on the ground ahead of me. I fire back and get a hit.
I just like knowing that if I see someone at 150feet behind a fir tree I can hit them. But this is just me.
The best advice I can give to the new players who ask about upgrading is to keep their guns stock. Less wear, less tear and has better re-sale value.