I think that Gaussian splatting is generally better, as the Gaussians are smoother and easier to optimize, if you can use them.
Things like triangle splatting are useful if you have to integrate into an engine that only support triangles. But with modern graphics pipelines, you can implement Gaussians quite efficiently, including newer techniques like Gaussian point splatting that can scale up seamlessly to enormous scenes:
* Video: https://www.youtube.com/watch?v=2AWv_nIfp-U
* Paper: https://jorisar.nl/gaussian_point_splatting/gaussian_point_s...