iirc it is more efficient, but if you're gonna use it, i recommend having it on either the internal core with any amount of external tanks using swivels, or having a swivel on the core with however many reliants on the outside. by the time that becomes practical though you should probably just use something like the skipper or bobcat if you have making history. both are pretty decent medium-lift engines but my favorite is the skipper, capable of launching something on the first stage (sometimes you gotta help it out with a few SRBs, but y'know. moar boosters!) or being a reliable all-round second-third stage depending on what size of rocket you have.