I am going to get flamed for this to no end but here goes...
I have both controlers in my system current system. I have the Highpoint integrated into my motherboard, the Abit KA7-100. I also have a Promise Ultra 100 card (non-raid) that I have a 75GXP and my burner on and it works great. I have two 75GXP 30gb on the highpoint channels ruuning at ATA100/RAID 0 as my main drive. I have been running this same RAID array on the highpoint for almost a year now with no problems. I even installed Win2K as my main OS directly onto the RAID drive. I just loaded the drivers for the highpoint and setup did the rest. Both controllers even share the same IRQ with no problems. The Promise are definately the preferred controllers because highpoint had alot of problems with the ATA66 controllers and now they are generally considered crap by many. I have heard of no problems with the ATA100 one, but because of the ATA66 problems everyone says they all suck. Anyway, both work great and the highpoint actually outperforms my Promise by a slight edge with the newer drivers, but nothing that is noticable. One other thing to consider is that the highpoint mostly comes integrated in mobos by Abit, Epox, etc. while there is only one card form of it that I know of...the Abit Hot-Rod or something. The Promise comes in mobos as well, Asus, MSI, etc., but it is more readily available in card form at most computer retailers...it is only like $30 for the Ultra100 at buy.com. Anyway, I would say that they are both good performers and any performance difference is nominal. So, I think your best bet is probably a Promise Ultra100 as it is much easier to get your hands on and it is very cheap. Good luck.
/puts on flame suit