I have an old K5 Wee and test rode the Wee2. I've never had a Transalp, but I did look into buying one before I got the Wee. I'd need a lot of persuasion to buy a Tiger with what I've heard about the dealerships and the niggly little problems the bikes have.
My old Wee will tick over to 90 000 miles in the next week. I've never opened the engine up and the worst problem I had was a failed servo motor for the secondary throttle valve actuator. I could still ride it and if I paid more attention I could have removed the secondary butterfly valves and avoided the extra fual costs (doubled it!) that I had until I got some replacements. I bought a complete throttle bodies assembly off an SV650 which cost me £130. That's the most it's costs me in almost 60k miles other than the usual servicing and running costs and any mods wanted. I would recommend a Madstad to sort out any screen issues you have, you can spend a fortune on trying different screens, but in the end the Madstad will fix the issue. Two up the old Wee does the job, don't expect phenomenal acceleration, but the fact that you don't have that kind of acceleration keeps your pillion happy. Don't get me wrong though, the engine pulls well if you make sure you're in the right gear. The sweet spot for cruising seems to be somewhere around 85 (kph, occifer!) on the Wee with standard gearing, but it will do 95 if you want it to (the comfortable speed will depend on your screen and helmet setup. I have upgraded the fork springs and a put a stiffer spring on the rear. I don't think you will need this on the Wee2, maybe just a rear spring if you go two up a lot and you carry some emergency supplies around the waist. As has been said, change those Trailwings and get Anakee 2 tyres on it.
Having ridden both I would recommend that anyone who can afford to buy the new Wee2 does so. The little tweaks were done in the right places and it is the better bike. If you are on a budget then get the best condition old Wee you can find, anything with under 30k miles on is still 'just run in' as far as I'm concerned. They are gems for the money you get them for. Even having ridden the new one the difference isn't enough for me to want to part with any hard earned just for the little, but noticeable, extra you get.
I
strongly recommend a test ride, but on a warm dry day so the tyres don't affect your confidence in the Wee's handling. The handling is really quite good once you've settled into the bike and with the right tyres on for our weather conditions (generally cold and/or wet.)
ps. Ooer... that longer than I meant to make it, that happens quite often