front so you can get a good grip. instead of having to grab it from a difficult angle
front = just grabbing it and pulling.
back = having to get under it to pull it making it more work imo
but then i suppose it depends on the toilet paper too. it if doesn't bend at the end it can make it awkward to pull
but the toilet paper you seem to use looks like it would be better to use the front way
as you can see in your second picture, the toilet paper is more flat against the wall which would make it more effort for you, whereas the first one you can just pull
infact in your second picture, it looks like you could chip a nail under the tiles if you weren't careful enough. and that would be the toilet paper's fault for being so flat