Usage of "is" before a present particple

Dear all,




I would like to inquire over a question boggling my mind just today. I have just submitted a write-up on a research I am working on at the moment (hence the need of a formal English representation), and the paper came back with a few corrections, one which made me rather curious:





[....]grouped under two categories of methods, one involving evaluators and experts [etc..], and the other involving real users [etc..]

What he recommends:
[...]grouped under two categories of methods: one is involving evaluators and experts [etc..], and the other is involving real users [etc..]



PS: I am not allowed to divulgecertain contents of my write-up.. Pardon me on that.

May I know which is more suitable for my form of write-up, or which is more grammatically precise?

Thanks, any advice is very much appreciated.