Do I Need Compressor 4?

I'm trying to decide whether or not I need Compressor 4.

I have been editing in FCP X for the past few years, and up till now have had no pressing need for anything more than what Final Cut offers in its share menu.

However, I have recently begun using Vimeo for all my Online distribution, and i am also needing to produce DVD's.

So i have been looking into getting Compressor for the last couple weeks, but i haven't as yet, as i can't see exactly what it's going to add over the FCP X share menu.

Basically what i need to know is the following...

1. Will Compressor 4 improve video quality and file size when exporting for Vimeo?

2. Will Compressor offer me more manual control of Bitrate settings?

3. Is the DVD export in Compressor better than the one in FCP X?

I am using FCP X version 10.1.4 on a Mid-2011 iMac 27"

My Final Cut Libraries and all other related media is stored on a Drobo 5D connected via Thunderbolt.

I also have access to a Late-2013 MacBook Pro Retina 15", would this, or the iMac be better/faster for exporting?