many times onboard RAID will be faster than a discreet RAID card since the onboard utilizes your system's CPU and memory (both of which are faster than most discreet cards).
i used discreet RAID in servers for 15+ years before getting onboard RAID in my thinkstation (which has both an intel ICH9R and LSI 1068E chipset). in three years i haven't had a single issue with SAS drives on the LSI controller. in fact, i'd say the only limitations are the lack of BBU and the inability to do live migrations—neither of which have proven to be an issue for me over the years. i haven't used the intel ICHR but can't say i've read about any major problems on this forum or anywhere else on the web. intel's RAID solution seems quite stable.