One of these fintech names has a far more promising future than the other, which hitched its proverbial wagon to the wrong star.Does your portfolio need a bit more exposure to the fintech space? There are plenty of great options out there, although payment technology platform Block (XYZ -0.45%) and online banking outfit SoFi Technologies (SOFI 1.02%) are a couple of investors' favorites right now. Either would likely work well enough for you.If you've only got room for one of these holdings at this time, ho ...