Tom,
I'm looking at getting a Sabco RIMS Wizard and have looked at the HERMS. There's a bit more plumbing for the HERMS that I don't want to do at this time. I have Sabco kegs so it seems like an easier refit to my current 3 tier gravity system to get the Wizard and fittings. RIMS appears to do a better job at temp control than the HERMS which I feel will give more consistent batches. The Wizard with the upgraded Unitronics V350 controller will allow for the saving of brewing sessions with data captured from the session. You can also do uploads/downloads from a PC so I can build my recipes off line and load them into the controller when ready to brew. I found this on
http://www.homebrewtalk.com:
HERMS
Pros: Relatively simple complexity. No danger of scorching the wort.
Cons: Requires a pump and heat exchanger coil. More difficult to use if you want to maintain temps and then raise temps.
RIMS
Pros: Easily maintains and raises temps.
Cons: More complex to build than previous methods. More difficult to operate manually - I think these systems are typically automated. Heating element can possibly scorch/caramelize wort.
I hope this answers your question.
Bill