There are tons of comment forms that are available out there and here are a few. I've included pictures of the comment forms and my thoughts on each.
Blogger Default Comment Form
It's okay, in my opinion. It's easy to use, accepts HTML and all you need is a Blogger/Google account to comment. However, there's no option for notification of a reply back to your comment, which I do not like. Also, it's looked pretty much the same since I started using Blogger (circa 2009). It's a tad clunky for my taste.
The reason I still use Disqus is because it's smooth and it's interactive. You get notifications when someone comments back. Also, you don't need to have a Disqus account to use it. You can use your Twitter, Facebook or Google+ account. The spam filter is quite good.
A negative side to using Disqus is that unlike the Wordpress comment form, you can't link your name to your blog and have your picture show up.
Also, do you pronounce it "discuss" or "discus"?
I like the simpleness of the Wordpress comment form. You don't even need an account though I have one. All you need to put in is a screen name, an email and the link of a website if you have one. Alas, it's not available to Blogger users.
screen cap of the comment form on a Time.com article
I first found out about Livefyre when Time magazine's online site switched over from Disqus to Livefyre. It's only available on Wordpress, Tumblr and custom blogs but according to their website, they're working on a version for Blogger. It's has similar options to Disqus, however you can sign in using more accounts.