I choose TopGear but it depends on the issue (cover & content).I even buy back issues if I have a chance to browse its content
I only buy C! annual buyers guide (for technical infos and other car-related topics).

On C!:
The Good: -same with number001 post
The Bad: - 2008 issue is much better than 2009 copy
- some figures are not accurate and not complete especially on the specs

On Top Gear:
The Good: -cheaper price, contents' ok
-better-written articles*, Botchi's section in particular
The Bad: - worse advertisements** than C!
-buyers' guide lacks other important informations

*The issue featuring the new Forester is the one I like most (not sure what volume # & month). It includes other articles of the Lancer EX and a nice piece on the Vios J (contributed by Conrado deQuiros).

**Although Tidus' is right on thick C! mag advertisement, TG has the worse one. An Oris watch endorsed by,say, an F1 driver is fine. On the other side, TG' staff qouted "a thick buyer guide is a waste of trees", but the magazine's page posting full-page photo of the 'Philippines' ***iest...' whatever and condoms are nonsense ads for a car magazine. I thought the latter is an 'aftermarket airbag replacement'.
Since that was, so far, my favorite issue, I just tear-off another page/insert of a credit card ad/application form and covered those two ugly pages.