Personally I prefer Buffer of the two. It seems smoother and allows you to buy the platform level that suits you the best. I found that I was able to see more before signing up to Buffer than Hootsuite as well. You can have one of each profile on Buffer for free, whereas you've got to start the trial with Hootsuite to see anything.
I like the fact that Buffer is more geared towards actually scheduling tweets to go out when you're not able to be there than anything else. I like that it's really simple to use and you don't have to have all the unnecessary extras around like you have with many of the social networks themselves. I find half the time the things they add really aren't necessary, so a nice simple platform is great in my opinion.
It might be more to do with the fact that Buffer works better with my phone more than anything else, though. But then I also have an ancient phone that needs to be replaced.
I never could get the hang of Hootsuite either to be honest, as much as I wanted to. I've heard great things about it. I did like the fact that you could see everything rather than it being mainly for scheduling posts though.
If you're just managing multiple twitter accounts, I actually prefer Tweetdeck to either of the above options though. You can have pretty much unlimited accounts on there (I've got around 30 at the minute on there for various different things and have never had any issues). It's also free which is a great bonus. That being said though, it is only for Twitter and if you're wanting to utilize multiple different social media platforms then it probably isn't going to work for you. There's no app for Tweetdeck either so if you're hoping to use it out and about you'd have to sign in using the browser. For me this isn't an issue, but I know it could be for some.