At the end of the day it all boils down to if you prefer to start with RMCs skill list that is lacking lots of essential skills and add skills until it works or if you want to start with RMFRPs complete lists of skills and trim it down until it fits you desired style of play.
OR...you could start with RMC's list of standard skills and secondary skills, and trim it down from there. I use around 44 skills total. I dislike the degree of discrimination in RMSS - I run a more open game, and rather than parsing an activity down to determine if a character has a specific skill that fits, I tend to give the benefit of the doubt, and allow them to try something they already DO possess. I find nothing "essential" lacking in RMC's skill assortment. It all depends on how broadly you interpret each skill.
That being said, RMSS has some strong points. The HP and PP progressions are much better IMO. Race-based, not tied to stat (as in the case of PP's for RMC). I like the rate of stat progression from RMSS more than RMC, but I just use a different homemade table for that for my game that gets me what I want. RMFRP adds the stat bonuses together, while RMC averages the stat bonuses, so for RMFRP, you have to make sure that every skill has an equal number of stats that affect it (3), to get consistent stat effects across all skills. Of course, you can use something like ST/ST/ST, to get a single stat as an effect, so that's not necessarily a deal breaker. But, if you want a skill that's equal parts ST and AG, for example, rather than simply averaging the bonus as for RMC, you have to do a little trick, like adding 2 stats and multiplying by 1.5.
Spell acquisition is much better in RMFRP, but again, it's an easy thing to bring over. Some folks like the more complete spell lists from the RMFRP books, but since spells are basically interchangeable, there's no reason you couldn't use RMFRP spell lists with an RMC core game.
So, for me, I run an amalgam of concepts anyway, and both systems have positives and not-positives. I do agree that the biggest difference between the two is the set of skills, and the core approach to them. RMFRP is simply more record-keeping than I'm willing to do for a casual friendly game, especially when I'm going to have to try to find a way to make the adventure work with what the players DID spend points on, not what they could have developed.
