Facebook's default app has never won a lot of fans because of its slightly buggy performance. Facebook Web gives you another way to view your feeds, but it doesn't do much to best Facebook's default app. The only improvements it gives you aren't noticeable and aren't worth the ads.
Since this is a Facebook viewer, you'll have to log in with your Facebook account to use it. It presents a Facebook layout that closely mirrors the one you're used to with a few changes. The most noticeable change is the ads on the top of your feed. You can remove them for about a dollar. The less noticeable, but so much more useful, change is the reminders for birthdays and events sitting at the top of your feed. In Facebook Web's settings menu, you can change whether the app shows your feed, inbox, or a specific page when you open it. The app didn't seem noticeably faster than Facebook's own app over cellular or Wi-Fi.
If speed is your main concern, you'll be better off sticking with Facebook's default app. However, Facebook Web has just enough niche features that it may steal some people away. It's up to you to decide whether the banner ads are too much to handle, though.