First off, welcome to the forums. Secondly, all birds are high maintenance. They require special food, cages, perches, constant care, such as feeding, watering several times a day, periodic grooming like nails, beak and wings and daily cleaing of their cage.
Low maintenance pets would be cats and gold fish, especially if you live in an apartment or condo. I WOULD NEVER RECOMMEND A BIRD FOR APARTMENT DWELLERS! But with that being said, here's my opinion on both Cockatiels and Senegals.
I love both species, both make very good starter pets. Cockatiels if well cared for can live up to 20 years and Senegal up to 30+ years. So you need to take that in mind.
I have owned Cockatiels in the past and they for the most part are a bit quieter than Senegals. But that has only been my experience. Some folks here will tell you they own a Senegal and they never hear a PEEP out of their bird. But I can tell you from personal experience, my Senegal is a noisy bird. She will make several noises through out the day, most notibly a squawk that can raise the dead. She doesn't mind using it either. She will squawk several times through out the day up to the point that I have to give her a time out which means I cover her cage with a sheet for like 15 minutes or until she quiets down.
She is a tad hyper, quite a bit more so than any Cockatiel that I have ever owned. But I have also owned Cockatiels that were just as noisy. If I were you, I would think twice about getting a bird while your living in an apartment because if you wind up getting a noisy bird, which the chances are great that you will because they are animals and chirping, squawking and screaming is what they do, you will find yourself hunting for a new place to live and could eventually have to rehome your bird.