I'm too bored to not aspy this up. So here goes.
Subscription pro/cons
- 1 click for all non-new threads you're interested in
- hides new threads you may be interested in
No-sub pro/cons
- See all threads, catch new ones you may be interested in
- N clicks + scrolling for non-new threads you're interested in
So it's clearly a use case thing, but I'd argue most people are checking old threads the vast majority of the time, so under that umbrella, subscription method is objectively better.
Additionally, the two methods are not mutually exclusive. So even if you want to check for new threads a lot, you can still do that. It literally does not make sense to not use subscriptions if you just want to check old threads.
EDIT: An important point I forgot: the frequency of old updates vs new threads. It's not even close. You're just an idiot if you're looking for new threads at the same rate as you are checking updates to old ones.