Personally, I'd prefer to see playthroughs only. I think most people should shut the hell up and just play the game (and be GOOD at it while they're at it, it's horrid watching people struggle through levels), UNLESS they're actually good at talking/narrating, and better yet, professional type people like AVGN. If they can make it entertaining to have to listen to you speak, then go for it. If not, just show the damn gameplay and leave it at that.

My personal thoughts exactly.  Sometimes when I just want to watch a game, someone let's the game run while explaining what they're going to do before doing whatever it is that they're going to do. They could have already been done with it by the time they stop talking.

The reason I ask this though is because I've just started putting some videos on Youtube again though and someone I know said they'd rather watch let's plays so I thought I'd ask.

Maybe I might appease some people by doing a let's play with very minimal talking and mostly gameplay.   Or I could put just gameplay, then do some video reviews of the games afterwards.

Gameplay. Most commentators are annoying. I dont really watch either one though but I found a video of Pewdiepie ruining To the Moon -_-

I like let's play only if the person playing is interesting and funny.

Well I prefer to watch speedruns so I guess gameplay but commentary helps for some of those. Only let's play I like to watch are informative or funny.

Gameplay-only if the game is heavily focused on immersion (Dead Space, The Last of Us, Beyond: Two Souls and the likes) and commentary if the game is light-hearted.

World of Longplays is a great site for just seeing gameplay, that people are GOOD at. Don't get me wrong, if someone wants to just show themselves playing a game if they're NOT great at it, then that's what Twitch and streaming are for. If people want to bother watching a live stream of someone die a bunch, that's on them. But World of Longplays is usually speedruns or playthroughs where people know what they're doing.

 Let's plays can be pretty good when  the commentator is entertaining and  good at the game he/she is playing.