Which one do you like more? ABRSM or RCM?
I am currently on Alfred Adult All in one level 2 and have been thinking of moving to an exam system - only for syllabus and structure. I do not intend to take exams. I would like to learn more Classical music and feel an exam system structure might be more enjoyable than the Alfred book.
Do you have any suggestions?
Either would be fine for developing all-round classical skills.
Choosing which one is a moot point as you're not doing exams, as they are very similar (if you bear in mind that ABRSM grade = RCM x 0.8). Don't forget it's not all about the pieces (plus studies for RCM) that you learn - it's all the other stuff too: scales & arpeggios (N.B. not all at once but more added gradually at each grade), aural skills and sight-reading. And music theory - again, commensurate with each level. Not all at once: no point learning stuff you won't be encountering or using for several years. Much better to properly assimilate each and everything you learn, because you're playing it and using it, rather than as an abstract theoretical construct (like learning E=mc2 without understanding how you could use it in practice, nor its implications).
When you've forgotten all about the pieces you once learnt at each grade/level (like I have: I can't remember a single piece I learnt for any of my grade exams, nor even for my diploma exam - I just wanted to keep moving onward and upwards as my skills improved, and go on to pastures new: classical music is inexhaustible that way), you'll find yourself using more and more of all those other skills that you've developed as part of keeping up with the syllabus grade by grade. Like having the aural skills to pick out the harmony parts of Allegri's Miserere or pop bands like ABBA, and singing along (should you wish to accept the mission), or just supplying the harmony to a melodic line, should you be called upon to do so in an impromptu sing/play-a-long with a long-lost relative you've just found via FB; or being able to sight-read a Christmas song you've never heard or knew the existence of until someone plopped the score on the music rest before you could say: "Now, I'll take some requests" after a few too many vodka martinis and Joplins.
RCM consists much more repertoire, but do you study every piece in the book?
And ABRSM has very limited repertoire. Do you study only those pieces and then move on to next level?
And do you have opinion on comparison with overall cost for the two?
You shouldn't stick just to playing pieces used in exams for either board. Think in terms of having three pieces on the go at any one time, in different styles, at different levels of completion, and as you finish with one, start a new one. Don't stagnate on any one piece, even if you like it very much - you can always find more, and you can always return to it at any time, and play it better when you have better skills. (My experience when I was a student at your current level was that I soon lost interest with an old favorite when I discovered and learnt a new one.) You'll be learning some fifty short pieces a year at the lower levels, which is more than in any one of the RCM or ABRSM books.
With ABRSM, if you look at their pieces over a decade, the list of pieces are changed every two years, so you do have a wide selection. For instance, this:http://www.chsg.org.uk/_files/subje...evel-Music-Difficulty-Levels-Booklet.pdf
And all the non-contemporary pieces are, of course, free from IMSLP.