RMC is an updating and cleaning up some RM2 rules and from what I have heard new options on character creation and spells. The spells I have been told are basicly the same but they have added information on some of the vauge areas that reared thier head in the past few years.
The spells are basically the same. RMSS included a few new spells, IIRC, to fill in some gaps, but they kept the problematic and confusing spell type classifications. RMC kept the spells as they were in RM2, but changed the spell types to be more suitable for the spells and clarified how to resolve those types in a much better manner.
1)IMO RM2 tended to break down about 10th level, by this I mean it was not linear. I arrived at this position by teating and by talking to RM2 players who have been playing since the begining of the game.
If this were true, then RMSS would actually suffer from the same flaw as the core mechanics in both systems are the same.
However, RM2 had a tons of options, many of which people thought were core rules when they weren't, and it is possible that those options could of caused such a breakdown. In RM2, many of the options were not balanced against the core rules or other options, and so it is quite likely that they contributed to this breakdown.
In RMC, ICE is taking care to make sure that folks know what is and is not optional and to try and keep the options balanced as possible.
2) The skill system is a major difference fom RM2C to RMSS/FRP.
Yes, the skill system is one of the major differences. IMO, one of the mistakes of RMSS/FRP is that the costs are set on a per category basis, not a per skill basis. This required the old ICE to come up with a method of having better and worse costs on some skills than on others, and this led to the Occupational/Everyman/Restricted skill rules, which I feel are an over complication that was not required.
RMSS uses a tiered skill system (which is cool), but I also think that they went too far in trying to make too many skills overall (such as 4 skills required just for herbs). Then again, one of the principle designers of RMSS was heavy into skills, and in fact, I have been told that it was almost impossible to get into combat in one of his games (apparently he hated the RM combat system and never used it -- which would explain why it was the most untouched portion of the game when RM2 was revised into RMSS)
3) Single Stat bonues can have a bigger influence IMO in RMC than RMSS.
Not quite true. In RMC the single stat bonus is approximately 2.5 times larger than its comparable bonus in RMSS. However, in RMC, stats are averaged together while in RMSS they are added (and in RMSS, a single stat is often doubled or tripled when used alone).
4) RMSS/FRP puts almost a limit on skill bonuses, after a specific point you nly get .5 bonus per rank. In RM2 and I think RMC you can have very high skill bonuses. For example some of the people described in the MERP books People of Middel Earth have the balrongs OB in the 400's and its DB in the high 190's, going from memory. In RMSS/FRP I think they would be about 1/2 that, but I would be guessing.
The 0.5 per rank after so many ranks (30 usually) came from RM2 in the first place. And as for Middle Earth, that was just over powered to begin with, and yes, it did include some insanely high stats, but again, that was optional RM2 rules not core rules. The end result being that RM2 with its options is NOT really the same as RMC.
Progression Rates
RM2/C --- 5/2/1/0.5
RMSSFRP --- 5/3/1/0.5
RMSS/FRP actually gives a larger bonus overall at higher levels.
5) RMSS professions are viewed IMO as genetic templates when as in RM2 and I think C professions are viewed as your job. This might have changed in C but I an not sure but it did lead to many professions. In RMSS IMO you would need to creat a TP to do the same thing.
In RMC, yes they are templates, not jobs (the Gift Companion that is being worked on has Occupational rules, and I think that they rock). By my reckoning, there are about 26 basic "professions" (see my RMSS article on Irregular Realms on The Guild Companion for a better idea of my thought processes here). Everything else is just minor variations on the basic theme.
6) In RM2 you get bonus to skills on a per level basis in RMSS/FRP you get a higher skill bonus when you pick you profession but none per level. I think RMC has some optional rules that you can bypass the level bonus.
In the core RMC rules, you only get bonuses to combat skills, nothing else. There are options included, and some of those options actually replicate the RMFRP method of bonuses.
