Of those 3, I'd choose #2.
The video card is the most important thing to look at with modern games.
Memory can usually be added, but not graphics.
The ATI HD 4650 is midrange, the 5470 is low end and the 4330 is even slower.
Slower = longer battery life, but poorer gaming ability.
Unless you get some huge, thick 17" or 18" laptop that's upward of 7 lbs, you're going to get onboard graphics. The only difference is the chipset. Some motherboards have Intel graphics built in, some have Nvidia built in, some have Radeon built in, some have a combination of Intel and one of the others and switch between them.
I assume you're looking at used laptops at Dell to keep the price down.
Most current laptops have more than 3 or 4 GB of system memory.
Don't get a laptop with 512 MB or less of video memory.
There are some current adventure games that won't play well with less than 1 GB of video memory.
For a new PC, I'd choose at least 8 GB of RAM for a 64-bit operating system.
If you're getting 32-bit Windows 7, 3 GB or 4 GB is fine. Or plan to add memory -- check the user manual for the laptop and see how easy it is to add memory. Some of them make both memory slots accessible by unscrewing a panel from the bottom of the laptop, while other models put one of the slots under the keyboard, which requires more disassembly.