Upgrading: 500gb Ultrabay HDD or 8GB RAM?

[foghorn]

The set-up:
T410s with 4gb (2x2) ram, 80gb SSD.

I have about $100 to upgrade so I have to do one or the other, an Ultrabay HDD upgrade or 8GB of RAM.

The notebook hasn't been set-up yet but I plan on running a Linux distro.
I frequently use virtual machines (on a 8gb ram system) giving them 2gb of ram however, I noticed that I am around 3.1gb--hardly gooing over 4gb.
But the 80gb SSD is pretty small and easily to exceed. I don't think I'm going to upgrade it since it uses an nontraditional 1.8" drive.
I guess virtual machines both tax the hard drive space and RAM, so going with either one is a hard decision.

A RAM upgrade will run me at $60-70. And a Ultrabay HDD w/ 500gb will run me close to $100.
The Ultrabay caddy is one done by Newmodeus which is the closest you can get to OEM quality. The eBay stuff makes me weary. (unless someone else says otherwise).

Also, how well do virtual machines run on external hard drives?
Because the other option is to skip the Ultrabay HD upgrade all together and use an external hard drive.
I only use virtual machines for Windows applications (Autocad, Solidworks, etc.)

What do you guys think?

[kony]

Get whatever you need, if you don't need 8GB of RAM but run short on storage then HDD would be a wiser purchase, wouldn't it?

[foghorn]

I ended up upgrading to 8gb of ram. Since I'm running on an SSD, I don't want any swapping. I noticed with 4gb of ram I was swapping memory but did not go over 4gb.