I've had experience with Spotfire (although rebranded by a semiconductor analytics company) a couple of product generations back. My feeling is that it's a strong product with good interactive analysis features, that does many things as well as JMP, a very few things better (I preferred it's implementation of dynamically linked tables) but some things not so well. It's probably best to "suck it and see" if you're interested, although it has a steep learning curve.
However, I much prefer JMP overall because I find the scripting and automation of JSL is so much better. Trying to automate complex analysis flows in Spotfire was difficult to create, debug and maintain, and dealing with user input was also clumsy. It also didn't (IIRC) have anything similar to Graph Builder, which is so handy for quick visualisations.
And of course the JMP Community is an amazing and invaluable resource, which has helped me enormously!