I have well over 100Gb of music, and one of the great pains of that is when you encounter a UMS player like the X5. Thankfully, I use
j.River Media Center to fill the X5 which provides me with an iTunes-like drag & drop onto player interface. It's not quite as simple as the iPod + iTunes though, and there are frequent minor irritations... just as well that j.River is also a great PC-based player which IMO is far superior to the overrated Foobar.
I must be one of the few who thinks that ultimate possible sound quality of the iPod has been coming down over the last three generations, but most people run with low-impedance or / and low-cost phones in which case things will have improved on the 5G. It plays much nicer with low-impedance phones, and in fact the measured low-impedance falloff of the 5G iPod is virtually identical to the X5.
Sound quality is very similar as well, and anyone who says otherwise has not compared the two side by side. The X5's equaliser still behaves more predictably but the very apparent distortion on the iPod has gone. Sustained low notes can still cause the Bass Booster preset to distort though, although I can't get Latin to distort to the same degree.
With the X5, I use manual drag & drop plus limited playlisting, both in j.River. Even with j.River, it's still somewhat clunky on the playlisting side, and there is a dearth of a usable smart playlist options (j.River's Smart Playlist requires a programmer's mindset) so I don't use that a lot. For Podcasts, I have
Juice (formerly iPodder) running on the server which downloads Podcasts into a \Podcast\episode folder structure. This is then synced using
Microsoft Synctoy, and I've used
Autoplay Repair from Quickfind so that Synctoy (and j.River) appear as autoplay options when I dock the X5.
With the iPod, I mix and match prepared Smart Playlists with manually-filled playlists as well as a variety of Podcasts. I set the iPod to automatically update with these playlists. That way, I can mix & match manual filling and automatic selections. iTunes features the simplest way to do this I've ever come across.
Which do I use more? The iPod undoubtedly.