What's the difference btw the new JD rules and GMC-1 rules?

[Aman]

OK, there's lots of threads, but I am pressed for time these days so am begging the obvious question - for those of us with the old GMC-1 set, what is the difference in focus and mechanics between the two sets of rules.

There was a lot of talk and suggestions, and I plan to download and read the new rules, but what do those who know better than I have to say?

Thanks!