15" Macbook Pro with or without retina display - heavy use

I work in online marketing, and just about live on my computer. I have tons of photos, some videos and music, but also a lot of files that I access via a personal and a professional DropBox. I have a 1TB backup drive that I use for Time Machine. I also travel a lot for work, and currently am running out of room on my existing Macbook Pro, and am torn over which model to get next.

I currently have a 15" mid-2009 Macbook Pro running OS X 10.8.2

Processor: 2.8GHz Intel Core 2 Duo

Memory: 4GB 1067 MHz DDR3

Hard drive: 500GB

USED: 431GB (yeah I know that's a lot)

Here's my concern. I love how fast it was, but it's getting slow as I have more and more stuff on it. It's got some dings and dents from being carted all over the country, and I've had to replace the screen once (I cracked it..) so now there's some dirt underneath it that I keep meaning to clean but just haven't gotten around to it. I have the 1TB backup drive, but it's not easily portable. And I frequently (always) multitask, so need a computer that can handle having everything opened and running multiple programs at a time (5- 10 programs depending on what I'm doing). I have the glossy screen (holy glare!) and if I stay with the non-retina, would definitely get the anti-glare hi res screen.

Based on all of the above, which makes more sense for me to get?

15" Macbook Pro with Retina ($2,799)

2.6GHz Quad Core i7

8GB 1600 MHz DDR3L (do I need to upgrade to the 16GB? no, right, seeing as how I have just 4GB now?)

512GB SSD (concerned this won't be enough - do I just spend another $100 and get a portable external drive?)

15" Macbook Pro Anti-Glare Hi Res ($2,499)

2.6GHz Quad Core i7

8GB 1600 MHz

1TB Serial ATA Drive

Here's my last question - based on what I've read, the SSD is significantly faster than the traditional drives, is this true? If so, does it make sense to just go with the retina display and purchase an external HD so that I have more room?

Thanks so much!