I started converting my road bike into a fixie, and like most road bikes I have two chainrings. Consequently I also have two cogs that give me about the same gear ratio.

I could go with 53 and 18... or 39 and 14. I heard from a friend that going 53/18 may be a bit too harsh on my legs, but his legs and my legs are obviously not the same.

I haven't actually been able to ride on either of the gear ratios cause the conversion isn't done, but I'd like to know which is more ideal.

I never ride in hilly areas simply because there are no hills where I live. I want to be able to do tricks and what not (I'm converting it mostly for this reason) and I'm not sure if the gear ratio will affect my ability to do this.

53/18 will give you 77 gear inches. 39/14 will give you 73.
If your idea is tricks > speed. Go for the 39/14.
39/14 will give you slightly easier handling trackstands, wheelies, and skids.
wheelies = barspinzzzzzzzzzzzzzzzzzzzzz.

Both ratios give you very good skid patches. 14 and 18. or 28 and 36 if you skid both legs.
Either one wont make much of a difference.

Thanks for the quick response

I have a friend in need of a 18t cog, so I guess I could sell it to him and go with the 39/14.
I hope I can still manage to race cars down the street! Haha.

Its more impressive when your legs are blurred as you race down the cars