More active in posting

[aaron792]

I found that in Internet forum, the users from the forum that holds a smaller group of regular users are more active in posting.

I want to use the following sentence to describe the phenomenon:
It's interesting to see although forum A holds the largest number of online user, its members are not the most active in posting. On the contrary, users from the smallest forum, B, tend to post most frequently.

I am not satisfied with the parts underlined.
Can anyone suggest some more natural expressions?
Thanks in advance!

[RonBee]

Try:

Forum A has more members, but forum B is more active.

[aaron792]

Thanks, RonBee!
I will use yours~

[Raymott]

I found that in Internet forum, the users from the forum that holds a smaller group of regular users are more active in posting.

I want to use the following sentence to describe the phenomenon:
It's interesting to see although forum A holds the largest number of online user, its members are not the most active in posting. On the contrary, users from the smallest forum, B, tend to post most frequently.

I am not satisfied with the parts underlined.
Can anyone suggest some more natural expressions?
Thanks in advance!

"It's interesting to see that although forum A holds the largest number of online users, its members are not the most active in posting. On the contrary, users from the smallest forum, B, tend to post most frequently."

The underlined bits are OK as they are. "That" is not essential here, as you know, but in some long sentences, it can avoid confusion.