I personally would choose RH. They're well known in the IT world (as 
far as Linux goes) and have been very faithful to uphold Open 
Source/Free Software. Mandrake has done so in the past, but the 
recently released non-free software to boost their profitability. SuSe 
is a member of United Linux which has tried to close off GPL'd software 
with NDAs and it's sole purpose seems to be to compete with RH. If the 
free software issues don't matter to you then I guess this isn't much 
help, but if they do, RH is a great choice. And don't close off Debian 
as an option ;)
Harold