Just forget all sellers propaganda like 2.5 or 8millisecond etc,, things.
2ms monitor can be slower than 5ms monitor because those are just marketing things and response time is measured at the manufacture and each manufacture does it "kind of" differently. ;)
Just read this and you be much smarter http://www.tftcentral.co.uk/articles/response_time.htm :)
Btr.value is same thing, can't be sure.
Try to find real review from here http://www.tftcentral.co.uk/reviews.htm or other trusted places :)