At that price, zero lag will depend entirely on how you set up your phone. You're dealing with hardware limitations here. The difference between iPhone and Android in the occurrence of lag is that the OS limitations of iOS prevents lag (no true multitasking, interface is fully controlled by Apple unless you jailbreak, etc) and hardware at the leel of flagship phones. On Android however, being free to do with our phones as we want can also cause us to go over what our phones are capable of. For example, on a low end Galaxy Y, its very smooth functioning on stock configuration. But put in maybe 7 pages full of widgets and you'll see some lag now and then. On the contrary, a Galaxy SII will have no problems in a 7 page full of widgets per page due to the powerful hardware.
At that price point, you'll be looking at the HTC One V and the lower end Sony Xperia NXT line. If you go Gingerbread, there are plenty Samsungs to choose from. Honestly, Gingerbread vs ICS isn't important. I have no idea why you guys make it to be.