It doesnt really matter much unless running the 52 or the 42 with the rear cogs causes the chain to run at a great angle...which is bad mechinically.

Just a little extra - you could probably swap that cassette for one with a larger 28t cog and your derailler will probably still shift it just fine -- then you get a larger range of low gears and probably still get the same top end gears.

BTW- Don't post more than once - it won't get you answers any quicker and it annoys people.