O2 or Tesco Mobile?

At the moment I'm a very happy O2 Pay and Go customer. I have an online 'Genie' SIM that gives me 100 any time, any network minutes, 25 extra free as part of their 'Treats', 1MB free GPRS browsing and 10% back on my top-ups every month. For �10 a month, I find that very good value. And I get to keep that �10 as all of the stuff I've mentioned above is free. However, I have recently been looking at the Tesco Mobile Extra tariff and it looks impressive. They offer 10p calls and 5p texts to any network, and their tariff has no frills to it, which is what I like. I don't really want to leave O2 and I know that Tesco currently uses O2 for their network coverage, so if I make the move I needn't worry about losing signal. Would it benefit me if I move to Tesco or not? I send about 20 texts a month and I prefer to make calls. Thanks to anyone who can reply to such a fussy indecisive person like me.