I would go for the one with a title (and it's running on top of that). I think the fact that it's running AND has a title is worth the extra $150.
Heck if I find a deal like that around me I would buy it in a heartbeat.
A not running bike could have anything wrong with it. Sometimes it may be something simple and you get lucky, then all you would need to do is get it titled (heck it may just be an electric issue also). Other times it may be something highly involved and need an entire rebuild (how mechanically inclined are you?). Take whatever the previous owner says with a grain of salt. If it's something simple, why don't they get it at least running and charge extra money for it? (i know not everyone has the time, thats what they all say, but they want to sell the thing, just keep that in mind) If it does require a lot of work then you have a lot of time and money you'll need to put into it on top of getting a title, which depending on your state may be easy and it may not be.
Not saying that the 350 is in perfect shape, it will probably need some work too. But if the bulk of the problems are electrical that's not a big deal. At least it is running and has a title, which means you will probably be riding it much sooner than the 450.
The 450 will surely have more power, but what will you be using it for? Around town? Highway? Racing?
I would just figure out an amount that you want to spend all together, say $1500, if you can get a 350 for $450 then you have $1050 left to spend to fix it up and do what you want with it. If you go with the 450 then you will have $1200 left to get it running and titled and fixed up how you want. (just used 1500 as an example, i dont know what you have in mind)
With the 350 you will need to address the electrics and then basically fix it up/mod it how you like. The 450, you will need to get it running then fix it up/mod it how you want then get it titled. If you think it's worth it for the $150 (which will end more than an extra $150), that's up to you.
I have a 450 myself, but in the exact same situation I would go with the 350 simply because it is running and has a title. Even though the 450 is cheaper up front you will probably end up spending more on it than the 350 in the long run, but if you want the extra cc's and are willing to put the time into it, go for it.
