Buddah caves (Pak Ou) or Khuangsy Waterfall? Leave tomorrow

So which on would you sugest is better if only to see one of them in one day???

Or, i consider to se both with a scooter. Has anyone done the scooter ride to Pak Ou?

Leave tomorrow, appreciate replies asap :)

This is a very easy decision. Pak Ou caves is just a bunch of dusty Budda figures in a dusty cave, not at all worth visiting in my estimation.. Although the Ou is a beautiful river, but mainly if you go farther up.
Khuangsi waterfall is gorgeous, one of my favorite places in Laos. However it is only made very special if you go for a swim in the very highest pool.. To get there go up the wooden steps on the left side, at the platform about 1/2 way up walk up the gully. It will get a little steep but the limestone is very grippy on your shoes, so you can climb up some small waterfalls and get into a beautiful grotto. You can swim in the pool and look out over the 200? ft drop. Also go into the cave behind the waterfall.

Pak Ou Caves is interesting but if you have to pick on, Kuang Si waterfalls is better choice. I’ve rode a motorbike to Pak Ou just for the thrill of it. Very good road but it does required getting off the main route 13 about ¾ to Nam Ou River. You will need to hire a boat to get you a cross Mekong to the caves.

I'd definitely chose the waterfalls over the Caves. The Buddha Caves were a bit dusty and didn't look as cool as they did in the photos. The waterfalls however were gorgeous! And there were so many of them. I did see tourist options to go to both in one day if you really wanted to...