I tried an xps last year with an i7 and it was slow as well. Turns out it was thermal throttling like crazy. Returned it right away and just stuck with a MacBook Pro. Do miss all that ram though.
Thanks for this tip. I did some digging and found that even on AC power, the thing was set by default to throttle down to 5% CPU power whenever possible. I guess there's some ramp-up latency when demand hits, and that was creating the performance problems I had. After setting the min CPU at 100%, it performs almost as well as my 3 year older MBP.
