ISA MFM disk controllers

Anyone remember the difference between the various Western Digital MFM disk controllers? I've got a few in front of me right now, and I'm trying to figure out which would be the best for this Compaq Portable 286. I've got the good ol' WD1002A-WX1, and what looks to be the bigger verison, the WD1002S-WX2, then another, even longer card, the one that came stock with the Compaq, the WD1015-PL03. Now, here's the dilemma. The stock card won't respond to the usual debug commands - they just freeze the computer. The original 20mb 3 1/2" Miniscribe hard drive is dead (won't even spin). I am going to replace it with a similar 3 1/2" form factor drive - the NEC D3142. (43mb! Woo!) I already got the drive formatted and working on the small WD1002A-WX1 card, but it's been a while since I worked with MFM controllers - and I seem to remember the WD1002S-WX2 being faster or something. Also, I don't remember the calculations for optimum interleave, I used 3, since that was the default.... Pointers? -Ian