If you want a great mahogany soprano, don't get one of the Mexican Martins. I've tried a lot of them, and i own one. They are pretty similar to production ukes from Ohana and other mass makers. You can get a decent one, but if you are looking for something more than a mass produced uke - don't go there. On the other hand, you might get something better if you get one of the American made ones, the S-2 or S-3.
You cannot go wrong with Kiwaya. Wonderful sopranos. I own one of the laminates. They hold their own with well-made customs. Fit and finish is superb, playability, tone, the shoe package. The main reason I don't own a solid wood Kiwaya or one of their higher end models is that the laminate one I own is so good. One of my favorite ukes.
Custom is another can of worms. I've never seen a Timms, but his reputation in these parts for good Martin copies is high. In my experience a custom can be extraordinary, especially when it comes from an experienced builder. It can be a great value if you get lucky. On the other hand, custom can also mean over-priced, mediocre or even wretched. You can see mistakes and misjudgments on a custom uke that will rival a dimestore toy, and you can get amazing sound too (sometimes both on the same instrument).
Then there is vintage. You will find passionate advocates of vintage, people who will tell you that nothing is equivalent to a vintage instrument. Over the years I have chased various vintage instruments because there is a certain emotional connection to the past that comes with them. But, my best experiences as a player come from modern instruments. They are more consistent and reliable.
