I would be inclined to use the 6th Edition because it is up to date. The book is based on the joyo kanji (the set of kanji that the government specifies to be taught in schools), and that set got a big update a couple of years ago.

On the other hand, if you have a paper copy of one of the older editions then you won't go too far wrong with that. There is a pdf document available with the supplementary kanji that were added to the 6th edition.

RTK3 covers less common kanji and I wouldn't consider doing that until your Japanese is at an intermediate stage. Some people like to pick new kanji up as they go along, others to study them en masse in advance. RTK3 might appeal to the latter group. Note that the updated RTK1 contains over a hundred of the more common kanji from RTK3. The latter has not been updated so there is some duplication at present.

Regarding the spreadsheets you linked to: "RTK1 Edition numbers compared" is designed to do just what the title says, i.e. compare the numbering of the 6th edition with previous ones. I have checked the numbers with the book indexes and they seem to be correct (of course it's possible the books themselves might have an index error). The keyword list is not from the 6th edition, but 99% of them match up (the author changed a dozen or so keywords between editions).

As for the other spreadsheet you linked to, it's not that I'm advising others to use it, just I think it will appeal to some. It's a list of mostly rare kanji that are components of common ones. Learning the rare one along with the common one can save time and confusion in the long run.

If you are using an Anki deck then get one with links to the "Reviewing the Kanji" site so that you can easily check out stories submitted by other users (the site uses numbers from older editions, so make sure the deck takes account of that). I'd also suggest getting the actual book which contains useful information and advice (and you can verify the keywords).

Thanks for your prompt reply, Katsuo.

I, in fact, do have the 4th edition. My feelings are probably similar to your own though; I would like to use the most up-to-date version. So far, my plan is to go through the book and observe the differences in my deck when I get to them.

I noticed that you posted in "RTK 1 6th ed. deck" ( http://forum.koohii.com/viewtopic.php?id=10054 ) and mentioned the perfect deck. I think, I may have it. I used an existing AnkiWeb deck and have included all the *correct* changes mentioned in the thread. The result is a deck that contains the 6th edition Kanji with correct numbering and the remaining kanji in the 3rd edition with numbering updated to correspond to the larger first book.

I would like to include the errata mention here ( http://forum.koohii.com/viewtopic.php?pid=19558#p19558 ), but unfortunately the numbering is the different. Is there a spreadsheet running around with the actually characters and their corresponding numbers?

I like your idea about links to RevTK. I don't imagine it will be too difficult to add them now that we know the simple way of referencing the character.

Thanks for all your help so far!