[stephenr]

Prioritise RAM over all else. It is impossible to upgrade later, and more is always better.

I would also make sure the SSD is big enough for what you want to hold internally for ~ 3 years - eg I use virtual machines a lot and ended up with an ExpressCard SSD for vm images as my SSD is only 128 gb. On new machines you don't have the ExpressCard option any more so it's buy upfront or get an aftermarket upgrade for the SSD if you want internal (read: portable, fast and and convenient) storage.

[otoburb]

Based on that advice, and if the OP has time, maybe it's best to wait for more M.2 PCIe SSDs to go mainstream (and cheaper) in an ultraportable/laptop chassis.