Just some added thoughts: one question is whether you intend to be a "one man band" or not - will you need live backing or are you just going to play piano live? How many keys do you require for your live gig ? (if it's more than 61 then the Tyros is out). Workstations like the Motif can cover studio and live gigs but they aren't as well suited to one-man-band things without add-ons like arrangers are. The Motif has no hard drive option for storing midi files for example, though it does have some external storage options. The Tyros (or the 9000 Pro in my case) is truly made for stage use, offering a wide range of stock options especially for entertainers like voice harmonization (the Motif offers this with an added PLG card). And arrangers allow live improvisation while maintaining the one-man-band aspect. If you are a performer primarily, the arranger is the way to go. You listed composing work as your primary goal so it sounds like the workstation should be your first choice. If you use it with a laptop then you'll have plenty of live gigging options as well and you can add things like a harmonizer later.

Personally, I play several nights a week but I also work in the studio several days a week so I have a 76-note arranger for stage use and I'm about to replace my studio Kurzweil with the more-studio-freindly Motif ES 8. Hopefully songs created on the Mo will be compatible with my 9000 Pro, and when I want to dress to impress then I'll use both boards on stage (the Pro/Mo rig!).