First I think about the music I want to play and the sound that would be the best for that purpose. After that, I consider the construction of the ukulele (materials-- not workmanship). If I want to use electronics, that may have an influence on my decision. I also consider string tension... do I want a long-neck version of the instrument or will I be happier with, say tenor rather than concert or soprano. For me, string tension is more important in the "sound" than the actual size. For example, I have one concert-bodied ukulele with a tenor-scale neck. I have lots of standard size ukes, too. Take a soprano, the string tension is lower than a concert model, but, if I want more the soprano voice and would like higher string tension, for a sharper attack, do I want to go to a long-neck and have the soprano body with a concert-scale neck?
What tone, over all, do I want? A rosewood back and sides will have better low and mid-range tone than a mahogany uke. Spruce will be brighter than mahogany and will not mellow as much as cedar with age. Cedar will sound bright at first and just continue to get more mellow and sweeter with age. Then there are the exotic woods, starting with koa, very punchy with clear tone. Mango is softer and sweet, but it doesn't carry as well as koa. Zebrawood, pretty new on the market is bright, but it is a thinner tone than any of the others mentioned thus far. Maple is bright and combined with a spruce top will be one of the loudest ukes you can ever find, yet played softly, it can be about as sweet and mellow as any instrument. Maple is usually laminated, so the solid spruce top is important.
Considering all of these things, all of the Chinese imports are competitive in price. Quality can vary, so, buy from a trusted shop, MGM, UkeLadyMusic, Elderly, etc... If there is an issue, a good return policy is vital.
In the "K" brand ukes from Hawai'i, Kamaka and KoAloha get lots of love around here. KoAloha is very loud, very smooth, and has become a very big player in just fifteen or so years. They are a can't miss and have a "better than the weather" warranty... pretty safe investment.