Which mobile reception is recommended for iPhone 4

I have ordered an iPhone 4 from Apple online store 2 weeks ago and am about to grab it.
I am deciding which reception to use.


1.
3-mobile 15 pounds/month 1GB internet 300 min,
2.
vodafone 20 pounds/month 500 mb internet 600 min,
or are there any other recommendation you would make.

Actually 300 min with 500 mb internet is enough for me, but my biggest concern is which one is providing stable and acceptable coverage and 3g internet speed in Birmingham.


Thanks