Clarifying a few inaccurate points:

The Colab model of "resources are free, just not guaranteed" model” that you mentioned is literally identical to Gradient: The free tier includes spare capacity at no cost just like Colab. You can upgrade to access high-end instances eg the NVIDIA V100. These additional instances do not have a max runtime as well. I can’t see how this would be a con given this additional option is simply not available in Colab.

Gradient does not have a $5 deposit for storage, the free plan does not cost anything. There is no credit card required. In fact, Gradient doesn’t charge for storage at all.