OldChook,
There are a couple of things to consider,
LapTops
They are portable
You can sit in comfort to use it.
They are only portable if you can connect to the Net by the use of a wireless card, usually built in now, but you need a wireless modem or wireless Router to send the signal.
You can't sit in comfort to use it if you or someone else trips over cords :Power, phone line or add ons like printer.
You can only upgrade the memory by using an external drive. I have had to do this so use an Ebox 320gig, before this I was constantly spending time deleting, (as well as my usual backing up to disk,) and then waiting while it Defragmented and tidied up. Then a week later it slowed to a crawl again. When I first got it I thought 60 gig was large enough, just over a year ago. !!
Desktop:
They can have a very much larger memory, both RAM and ROM, and can be upgraded, mine has 2 drives now, when working on a project I use C drive, the original is 80 gig, then move all backups to my 320 gig drive G, this way I now dont have to remove them and later put back things like photos, which I now load directly to the G drive.
Everything is permanently connected to it.
The operating system is now something you do need to consider, which ever you choose, If you want to use 2 computers, as I do, a laptop and desktop, make sure the operating systems are the same, it is almost impossible to move information from a computer using Vista to Windows XP, If you want to use Vista, as it does have some great features and add ons, like windows Media Centre, the same applies to the new versions of Word, Excell etc, you can transfer information up to the new one, you can't easily send it back to Windows XP in a readable form, also heaps of printers still don't come with Vista drivers on the disk you have to go on line and try and download an upgrade, if available, Even if it says on the box Vista compatable, that usually means by download, unless it says Vista on disk enclosed.
Well I guess if you were not confused before, you are now.
Any questions just ask.
Bleggy