I would advise against installing an environment mod on top of either TMO or RFB.
Good chance it will FUBAR the install. Both megamods are configured to work within the environment they come with.
As to which you should try - there really is no alternative than to use MultiSH4, and run both for a couple of weeks, see which one you prefer.
See here
http://www.subsim.com/radioroom/showthread.php?t=108215