Without a doubt for me its FRER (first response early result). They're not cheap but not as bad if you buy them on home-health-uk's website. (£6.95 for 2 as opposed to between £10.50 - £12.95 boots, tesco, etc) Postage is free and quick as well - 2 days free or next day for 50p. Bought all my opk's from here too which are cheap and work well.
I had a mare in January trying to work out if I was pregnant. I used one step cheapies (same website) and thought I saw a line so used a clear blue digi (so expensive!) on day AF was due and came up negative! (Meant to be 99% accurate) Then carried on using cheapies. Really faint line but not a darker line. So waited until AF was 4 days late and used boots as had run out of cheapies and had boots points to use (still didn't wanna spend money after cb digi). Both negative in the result time, then after an hour of googling, broke the tests open and could see a second line on both tests (using fmu and concentrated afternoon urine). Exasperated to say the least! Went out and purchased FRER after googling and using this forum and found that everyone said good things about FRER. Used same fmu that I'd kept in its container and it came up in 20 seconds and developed to DARK line in 1 minute.
Unfortunately I miscarried at 6 weeks so back in the game with you ladies this month! But I will now use FRER from now on!!!
Sorry the post is so long but thought I should share
Good luck to everyone TTC xxxx