I am a member of three hill-related forums.
I joined my first forum, back in 2002 -UK Climbing.
I stopped posting there, and have rarely visited UKC in recent years, as I got fed up of the almost constant bickering there. In 2007, I joined Scottish Hills. In 2009, I joined Walk Highlands.
I currently use both Scottish Hills and Walk Highlands, as do many others.
To date, I have definitely been most prolific on Scottish Hills.
I think both of the above sites have their strengths and weaknesses e.g.
Fantastic back catalogue of trip reports & separate fora for Munro, Corbett, Graham etc. - Scottish Hills
Ability to add routes to reports, up-to-date bug-free site, etc. - Walk Highlands
Scottish Hills is less formal than Walk Highlands. Justifiably so, as Walk Highlands is run as a business.
Both sites also have associated meets. I've attended both and found both good.
Is it 'loyalty' to stick to using one site or another?
Debatable, I'm happy to get the best from both
.