I'm launching a site that has pretty tough competition in the US, yet reasonably low compeition in the UK.

I feel that with a few months worth of decent link building i could rank a .co.uk in the top 3 google UK. This would bring in revenue while i tackle the longer task of the .com in the US.

However, i'm struggling to decide if it's worth me taking this low hanging fruit with a .co.uk or if i should just subdomain the .com with uk.domain.com and put in the extra effort to get it to rank in Google UK without a .co.uk domain.

Subdomaining would obviously get some of the goodness of the initial link building i do while ranking the UK into domain.com, but would take longer to rank in the UK.

Thoughts?

Edit: It's worth mentioning that the link building method i'm going to use makes it much easier to get homepage links than deep links, which will be domain.com, this would also affect the time it takes to rank the subdomain instead of the .co.uk

Edit 2: Thoughts on ranking the .co.uk then 301 it to a subdomain on the .com when it's ranking?