I'm doing research to buy a new laptop and I'm big into Logic and hundreds of gigs of plugins. I will have a 512 SSD that I will get for the main drive from a 3rd party but that is not enough space so I really need a uMBP so I can still optibay it. But if I were to potentially sacrifice a dual drive setup and go with a TBOLT external HD, what other downsides am I facing? I hear lag, what's the MR verdict on that? Ergonomics? Is it really that better that its incrementally skinnier? Retina, is it really that better compared to a hi-res uMBP 15? I use an external HD projector a lot anyway for video watching or dual screen stuff. Upgrades, can I buy a HD setup for regular price and at least upgrade the SSD myself? What else do I need to worry about? And I worry a lot. Am I missing anything??