Hello! I know this is sort of an old post, but I thought I'd post anyway!
I have two Budgies, Skittles and Nico, they're a very bonded pair who live together. I'm just going to go ahead and point this out, if you get a pair, your birds will most likely bond to each other more than you. Now, that doesn't mean they won't like you, they just prefer the company of other birds. In my case, I've got two bonded birds who don't exactly like me. However, most of the time Skittles enjoys shoulder time with me, and will get up on my shoulder voluntarily. He, however, hates hands! You grab him or even pet him and he squawks like crazy! Doesn't bite, just has a major freakout. Like most birds, though, he does enjoy head scratches. Though, that's just the personality of MY bird, your future birds will most likely have a totally different personality. My other Budgie, Nico, I don't know what he'd do without Skittles. Whenever I take him out of the cage and place him near me, he flies all over to place just to get to Skittles. You might sort of be hesitant to get a bonded pair now, but don't be! Overall, I'm actually really happy I've got those two bonded birds. I get to interact with them for quite a while, and then after that I get to watch them play around together, which makes me happy.
As for which species, I'd just say go with whichever you like best! I know Cockatiels love to sing beautiful songs, whereas my birds like to go "SQUAWK! SQUAWK!", but I've gotten use to their sounds. I think Budgies are better talkers, however, that does NOT guarantee anything. Both Budgies and Cockatiels can be very loving and affectionate! I hope this helps.....sorta?
I currently have two male Budgies, whom I love very much! I hope to soon expand my bird family and adopt more loving feathered friends into my home!