The cheaper solution sometimes beats the more expensive solution in almost every way. Our soap solution is an example. We spend all of about $35 on soap every several years, in the form of a gallon jug of Dr. Bronner's peppermint castille soap. I dilute it with water (about 1 part soap to 8 parts water) into pump bottles we keep everywhere we need it.
It's a great grease-cutter, it smells good, and it lathers more easily than bar soap.
Liquid soap doesn't travel that well (especially if it's subject to vibration.) But that's the only downside I can think of.
You can look for it in your local earthy-crunchy grocery store if you have one (you may have to special order the gallon size, though.) Otherwise, a web search turns up a lot of opportunities to order it.