Hi all
Well, I'll say depends on what you plan to do with it.
In my few years of experience with both kinds, this is what I can say:
FB groups:
1) Really bad if you plan a tutorial or help group, as the majority of members never ever use the search option, so you end up with members posting the same questions over and over again.
2) Fb groups are bad because all posts go down = get forgotten.
3) Fb groups are really good because you can get members fast.
4) Bad because you do own the database and can lose the group at any time.
Telegram groups:
1) Very good as a support system, I mean what's better than informing the members live and making them feel that they can reach you at any time!
2) Bad for Tutorials etc, as chat gets lost (same as FB).
3) Bad because you do NOT own the database and can lose the group at any time.
My personal solution is:
FB group to get people fast + Telegram group to keep them active in FB + a forum with very clear sections to keep all the posted info organized and to KEEP MY MEMBERS FOREVER.
Again it all depends on what you plan to do and what services products you are offering.
In my case, I always used them for support and exchanging ideas in very specific niches, that's why the 3 together are really good for me.
For the long term: keep your own data, don't risk your business on other platforms, I knew a few who lost everything overnight just because Mr FB or Mr telegram decided to cut them loose.
Hope this helps.
Cheers.