I upgraded to the Intel 5300 and would never go back. I had way too many connection problems with the Dell 1510. A lot of people have managed to get the 1510 working just by changing the channel on their routers, but that didn't work for me. I did try several times, with several different channels and various settings, but the few times I managed to get it to connect, our other computers were unable to connect to the wireless network because of the changed settings. In the end, I decided it was worth $20 to upgrade and stop the aggravation!
Aside from those issues, even without the third antenna installed I've found that the Intel card has much better range than the 1510. At home, I'm able to pick up twice the number of networks than with the 1510.
It's been a while since I upgraded, and I haven't really kept up with developments on the 1510 front, so it's possible that the problems I had when I first got my 10v aren't an issue anymore. However, I would still strongly recommend the Intel card.