I've googled this topic and found some people think you get the same number of experience points for quests and kills no matter what difficulty you play and some people think you level up slower on the higher difficulties.

I'm playing on Death March and for completing the quest "Precious Cargo" I got 8 experience points! I was expecting about 25!

I am hoping that maybe someone here on the gog forum would be able to give me a definitive answer.

If I get several replies some saying "yeah, you level up a lot slower on death march" and some saying "No, number of experience points gained does not depend on difficulty level", I'll laugh my head off!!! :-)

I think the harder the level played as in easy,medium,and hard always end in less experience points.This is common in most games.

Getting fewer XP points if you're a higher level than the quest is one of the worst things about the game in my opinion. I like open world games where you get to choose which quests to do in what order. The game is basically saying, "Do quests in the order the designers say or you'll be punished with fewer XP."

I think quests shouldn't have a level and just award a set number of XP based on difficulty.

Quests get easier when your character gets higher levels.
I'm not sure, but to me it seemed like the principle also goes for the main quest line, but slower.

No one tells you what quests to do in what order, with exception of most of the main quest line.
I prefer to at least visit all message boards first and get both the quests and fast travel point there.
You won't have all quests that way, especially the treasure hunt quests and witcher armor quests, but it gives you more freedom.

Thanks for all the replies, guys. I am now doing the Bloody Baron quest on level 4! I have managed to kill bears and bandits at level 6 (maybe some above that) and it would seem fair to get extra XPs for kills at a higher level but I don't think you do. Looks like I get 2 XPs for killing a wolf. Anyway I am determined to beat the game on Death March so I'm off to do a bit of grinding!! Looking on the bright side, it's an awesomely beautiful, absorbing game and you don't want to rush it.

From my experience the is NO DIFFERENCE AT ALL between "Story and Sword" and "Death March" when it comes to experience points. I ended the main-game at the same level regardless. As you already know what matters is your level compared to the quest level (the difference should never exceed 5 levels if you aim to maximize your experience as already mentioned). Side quests often give little or no experience, while contracts often give between 150 and 500 EXP on completion.

Make sure to visit all markers early on so you know all the available quests and their levels (you may also want to travel to Skellige a bit earlier for the "Following the Thread" quest if you are a hardcore min-max'er, but honestly it makes no real difference). In general you should not worry too much about your level if you own Blood and Wine. The experience you get for killing random critters in Toussaint is SO high, so even if you fall behind there is a way to catch up.