JDM B20 (B and Z) = same compression as USDM B20Z (9.6:1).
USDM B20B = 8.8:1 compression.
Why does the B20B with more miles cost more than the B20Z? Is the first B20 JDM or is it USDM?
You can get the B18B and sleeve/post it to 2.0L, then boost... the block cost after resleeving will probably come out to a few hundred more than the most expensive B20 in that list.
B20- great NA torque, wonderful to drop a VTEC head on, some nice pistons/rods, and go spank up on some people.
B18/turbo- more torque, but you have to deal with a turbo (maintenance), more noticeability (cops hear that BOV), more weight (not really that big of a factor) from the turbo setup. The cost is much higher too (but not too much more than B20/VTEC)... turbo builds realistically cost you a lot more than just the price of the kit.
Think about it, post back if you have more questions.