I really enjoyed both of them, but personally I like Demon Souls a bit more. I actually really liked the Nexus and having levels as opposed to the open world aspect. The games main strength is it's difficulty/punishment and rewarding feeling by beating an area/boss. So having to travel between the areas even with shortcuts just seems unneeded to me.
Also Dark Souls felt a lot easier to me. Perhaps because Demon Souls had already trained me to play the proper way? There's a few things about Dark Souls that make it a bit more friendly, for example the drake sword. You can get the drake sword VERY early on if you know how and it just makes the game a breeze up until you get a lightning weapon, which leads me to my next point. Lightning weapons are great because the damage isn't calculated by your strength or dexterity stat, but rather by the weapons on base damage. So you can save those points you would normally be putting in str and dexterity into something else like endurance and STILL do awesome damage. Which makes the game a lot easier imo. I know they lose their charm during New Game + but for the first time playing lightning weapons really take the edge off.
Though I do like some of the levels and boss from Dark Souls a bit more than Demon Souls, but as far as mechanics go Demon Souls > Darks Souls for me. But both are very good and I can't wait to see what's next.
