Which one is better between ProductHunt and Reddit?

It depends of what you are looking for. Reddit has a wider audience, and you can micro target the audience by focusing on specific subreddit. Product hunt offer an easy way to reach most its user: make a launch. That make Product hunt more time efficient, if you goal is to promote your product.

Well I voted for Product Hunt but both serve different purposes in my opinion. Product Hunt is best at preparing for your launch, finding like-minded people to connect with and actually make your launch visible. Reddit on the other hand is nice because some subreddits are used by a lot of people (r/entrepreneur or r/startups) so you can (smartly) advertise for your product of get feedback, etc

I went with PH because I feel like its functionality lets you reach much more people who can either give you feedback on your projects or even start using your products/services once you launch them. Also, from my experience people on PH are much more likely to stay on-topic than on Reddit. To be honest, though, I've tried Reddit for only a short period of time, but while there are many enthusiasts over there as well, I didn't find it that interesting.

I'd say PH has more people willing to try new things and give feedback. Reddit can be good if you are honest though and not too salesy.