I can't comment on Reddit but as far as imagefap goes I've had a lot of experience but a few observations:

1. The support is non-existent. Example, one feature allows members to upload vid clips. I've done that and it seems to have gone smoothly but then it's not there! Ask a moderator...crickets

2. Months and months go by and out of the blue you get a notice (automated) that a number of your pics have been deleted. Generally the reason given is a complaint but there is no way to query the type of complaint, who made it or even which photo is was! Don't bother asking a moderator...no response.

On the positive side they have drastically improved the uploading ability which is one of the easiest to use I've seen. Also the ability to communicate with other users is very good.

Generally, a pretty good site, much different from tumblr, not better or worse, just different.