I've been thinking about this as well although my primary reason for having a portable player is very much music based. Videos would just be a bonus that I might use on occasion. I currently have an iRiver iHP140 which is now a few years old.
It seems to me there is a fundamental choice to be made between either a small and light flash based machine OR a bigger and heavier disk based machine.
Starting with the flash based ones, it seems that generally 16Gb is about as big as they go at the moment. You can get a Sony 639 for just under £100 which gets good reviews but is only 16Gb compared to my current 40Gb. Yes, I know 16Gb is still loads of albums worth but is it enough?
The Creative Zen is also quite small and has an SD slot that would allow memory expansion but apparently the files on the card are not fully integrated into the player. They are available but, for example, would not be included if you set it on random play and files would have to be added separately to the player and the card. Now the 16Gb Zen is just under £100 (same as the Sony) but the Zen is also available in 32Gb for £150.
So, we now have a small and light player with something approaching as much storage as I have now for £150.
BUT, for £175 I could get an iPod Classic with a massive 120Gb 3 times what I have now. I could either carry 3 times as much music around or have Media Monkey transcode my FLAC library to Apple Lossless (assuming it does that) onto the iPod.
I am struggling to find any other disk based players. Maybe the Zune or one of the Archos type media players but if Im carrying something that big I might as well stick with the iRiver until it actually breaks.
So, to get back the the original point - given that I have a large music collection and ignoring any budget constraints I cannot see why I would buy anything other than an iPod classic. They appear to be such good value for money.