I chose paid simply because I know that most free web hosts are spammy, other hosts will even create popup ads on your website. This will look spammy to your visitors, especially if the Ad is not related to the content, so you might lose a lot of traffic.
Even paid web host companies like Hostgator, JustHost etc. are crap as well, more especially when you start to receive about 500 visitors a day. Your website starts becoming slow, as you grow your website and get about 700 visitors a day, then you'll start to get a lot of downtime (your website will be offline mostly).
So for a small/new website then companies like Hosgator are OK (not recommended though). Even if you're using paid hosting, make sure you're not hosting with any EIG company (google EIG company list to find them).