'A bit' is somewhat of an understatement
The typical SQL records for a Lr development are less than 100kb. A PSD file based on a DSLR raw image can be 100mb+. Smart objects are not references to the original file on disc, they're copies embedded into the PSD file so they're vulnerable to corruption every time the PSD is re-saved. If you work in Lr and need total security against loss of your developed images you only have to keep one 'permanent' backup of the raw file, then routine mirrors of the LRCAT database (which is small enough to backup online). I do commercial stuff that can never be repeated, so I'm paranoid about backups:
- CR2s from the cards go as-is to an external drive (using TeraCopy), then they're imported from the cards to my workstation in Lr as DNGs, only when everything's verified will the cards be reused.
- The external drives go off-site. I've only needed to pull copies once, when an SSD in the workstation threw a hissy fit - but if the office is eaten by Godzilla I can be up and running in an hour.
- The LRCAT databases are synced to the cloud every evening (using a batch script). Lr makes local backups automatically.
To highlight the fact that you're never touching the originals, in Lr5 you can work on developments even if they're not available - it'll take whatever you do to the Smart Previews and re-apply it to the original images when you mount the DNG/CR2 files again. When I'm shooting for a previous client I'll take their LRCAT (and the folder of Smart Previews) in case we need to browse the old stuff for reference - a catalog with 10,000+ images will fit on a USB stick. Also means I can play about with any of my photos in the airport lounge (anything to distract me from the free jelly beans ).
Of course there are thousands of things you can do in Photoshop that you can't do in Lr, but I'd never suggest using Ps as a default tool for developing raw files unless you have terabytes of storage laying about. Using ACR outside of Ps is another option (e.g. via Bridge) as it'll write an XMP sidecar file instead of a database record, but managing all those sidecars is a real pain and you don't get to use all of the presets and plugins from Lr.
Well, all being said...if you're doing things "non-destructively" in Photoshop, you're working with your RAW images as smart objects, and aren't making any changes directly to them there either. It eats up a bit more space ...
I wasn't implying that you work most of your RAW stuff in PS instead of LR. I just was saying that if you use PS, you would likely want to work non-destructively and use smart objects in PS.
I mean, these days....HD space is getting dirt cheap, and if you do have a PS project that had lots of layers, etc...I'd want to keep my options open for later changes, especially if working for a client that might want this or that changed, etc.
However, IMHO..the best workflow that I'm trying to do..is start in LR. Likely 98% of my images can be done there, if I'm careful enough to get as much correct in camera.
However, when something needs a lot of work...either to salvage or just for very creative stuff...then I'll do those images in PS...and likely as a smart object that comes from LR after I've done initial "development" there.
But no, was wasn't being a proponent for doing your primary RAW import and changes in PS.