QUOTE(Calex @ Feb 23 2011, 10:48 PM)
From what I can summarise, the differences are:
-Screen size and color display ability (3.5 inch 16million colors on Galaxy Ace compared to 3.2 inch 262k colors on Optimus One)
-Camera (5MP on GA compared to 3MP on O1)
-RAM (278MB on GA compared to 512MB on O1)
-Battery (1350mAH on GA compared to 1500mAH on O1)
-Wifi (WiFi b/g/n on GA compared to b/g only on O1)
-Processor (800Mhz Qualcomm MSM7227-1 Turbo on GA compared to 600Mhz Qualcomm MSM7227 on O1)
Hope this helps.

Ace is better in most aspect.
RAM is most argued by most people, but we will have to wait a full review to see whether the 278mb is sufficient onot, i guess.
Evrything is good enough for me, except battery life
Screen and processor loot power than op1, but smaller battert than op1
Samsung could have give us a 1500mAh battery and i guess the manufacturing cost will still be low enough to place a good price tag... too bad.