I would suggest checking the following link to compare the processor features:
If you need more detailed buying recommendations I would suggest contacting any of our Authorized Intel® Distributors.
You can find a list of Authorized Intel® Distributors at:
That is a tough decision. Either one would get the job done.
Looking at one benchmarking site, http://www.cpubenchmark.net/multi_cpu.html
The x5550 has the lead in preformance, ranked 27 out of 173, being a faster processor and using faster memory (assuming your memory support 1333)
The E5630 raked 37 out of 173, you get more cache so it won't have to hit memory as often and the power draw is 15W less (30 watts for 2) so you save on your power bill. Price wise I see both on Newegg with the E5630 running much less so you save money their too.
So it comes down to personal choice,
Which is more important to you, cost or a slight edge in proformance?