Desktop vs cloud: the underlying difference
NinjaTrader 8 is a desktop application for Windows. You install it, it runs on your machine and uses all its resources: heavy charts, complex indicators, backtesting and local automation. The trade-off is that you're tied to that machine.
Tradovate was born in the cloud. You open the browser and trade — nothing to install, from any device, with the same synced state. It's pure convenience, in exchange for less depth in analysis and extensibility.
Key question: do you value trading from anywhere more, or having advanced tools and automation? That answer decides almost everything.