Is the DMC collection really difficult?

Is it Dark Souls hard or God of War hard? I can handle GOW's difficulty not no DS's

It actually varies from game to game.

DMC1 is a bit closer to Dark Souls' style of difficulty in that ultimately the game boils down to your technique, managing your Devil Trigger resource and knowing your enemies. Enemies have a tendency to attack from off-screen, though they all have distinct audio cues (And large telegraphed attacks) to accompany them. You also have to be very deliberate as mashing on the attack button mindlessly is a good way to get yourself killed, seeing how enemies will parry and counter attack if you get sloppy.

It goes both ways though; you can absolutely wreck most everything in the game if you know what you're doing in no time flat as nearly everything has a hard counter, a easy enough strategy to exploit, or a critical hit opportunity you can set up if you're really good and you know what you're doing (Which you likely won't). Most of the bosses in the game are also rough with Phantom (First boss in the game on Mission 3) being a huge brick wall for most players.

DMC2's mostly crap. Dante feels more stiff and unresponsive and some abilities are cumbersome to pull off consistently (Especially shooting two enemies at once). That isn't to say the game is hard - It's ridiculously easy as Dante has absurd health and guns typically wreck everything, it's more tedious if anything.

DMC3 though is much more in line with God of War. From DMC1 to DMC3, the combat ended up going from this deliberate style game to an outright bombastic spectacle and the enemies were dumbed down a fair bit as a result. All enemies have one to three moves at most with obvious tells/audio cues that only attack while on screen. This means you can manipulate the camera to keep enemies from attacking. Dante is super responsive to boot meaning you don't need to plan a strike or two ahead, most of the time you're just flying by the seat of your pants as crap explodes all around you.

It's not brain-dead easy as enemies hit hard and bosses can be rough (At least up until about Mission 5 before the difficulty/learning curve starts evening out), but it's an easier game than DMC1 for certain. The only thing DMC3 really had going for it difficulty-wise is that 1.) Dante didn't really have adequate tools to fight the first three bosses elegantly when you encounter them and 2.) the levels were typically much, much longer than in DMC1. That second part isn't as much of a problem as they addressed that with the Gold Orb mode difficulty modifier that gives you reasonable checkpoints which weren't present in the original release of the game on top of bumping every difficulty in the game up a peg (So S.E.'s Hard is Original's Normal)

DMC1 and DMC3's really worth a shot though.