Hedgehogs are way better in my opinion because 1. I have one, you might say i have personal bias, but they are so easy to take care of.
2. They are adorable. HOW CAN YOU NOT MELT WHEN YOU LOOK AT THAT FACE!!!!!!!!!!! Guinea pigs smell bad, i rest my case!
I have personally never owned a guinea pig, although I have owned a hedgehog. Hedgehogs are very sweet animals when taken care of properly, although they do have some issues. For example, with a hedgehog you HAVE TO play with it every day if possible. Hedgehogs will become very antisocial very easily when not played with, which can be VERY frustrating for some owners because when a heggie comes to be this way, they will curl up into a ball and hiss. Next, they are very smelly! Hedgehogs aren't housepets, and clearly need to be kept in a cage/cut off area. When I had mine, he always sunk up his cage and it would need to be cleaned every day- every other day, which was overall a complete chore. Lastly, they can be very uncomfortable. Hedgehogs obviously have quills, and though when they're comfortable with their owner the quills go down, they can be very uncomfortable to hold and/or play with. Hedgehogs are exotic animals and if you want to have one as a pet, DO YOUR RESEARCH and be aware of the specific care they need.
They are easy to take care of and you don't have to be home to watch them all the time. They are also not very picky on food choices, so they can be early taken care of. During they say while you are at school they can sleep and do what they need to do without 24/7 watch.
I actually have two guinea pigs, and a hedgehog. And I think that guinea pigs are super cute but hedgehogs are adorable as well. Like when I clean their cages I would rather clean Hovi's (my hedgehog) cage way more then the piggies. Because I think guinea pigs smell worse then a hedgehog. Now don't get me wrong, I love all my pets, it's just that Hovi is just easier to take care of, and easier to clean. Because if I don't clean the piggies cage every other day, my room smells like a zoo!