I donāt have any experience with Blender, I heard good things about is, but also followed by āpretty good for a free appā, so I canāt share any insight on it.
About Modo:
I worked in many poly/subD modeler before (Silo, Max, Maya) and Modo was my last stop so far, for modeling has been a huge improvement in terms of fluidity (how fast tools are, selections, etc), precision (you can work with lots of numerical precision so you can prong things to CAD with a lot of confidence) and really powerful form creation/exploration tools like actions centers, morph maps and falloff.
@mcvltd point about stability is true. It was a crashing piece of shit until version 801. Now itās a lot more stable in every release, but if you are used to the stability of Rhino or Photoshop, wellā¦ it wonāt happen. I say in heavy modeling days you will get 1-3 crashes a day (my guess blender will be a lot worse).
Another thing to keep in mind is the new procedural modeling (iām just starting to learn that). That can also give you a lot of flexibility. more info here: https://vimeo.com/165476850. And here: https://vimeo.com/ondemand/modo4htoo
I havenāt used this stuff yet, but it seems to be well developed and mature.
Thereās also Meshfushio to add details and explore variants in Modo. That got a lot of hype. But I have not been successful getting it to work in complex geometry. Itās still raw and unstable. But the day this works well it will be pretty cool: https://vimeo.com/186287572
Last thing: the UI is deep, and lots of clicks/tab/menus. Itās a total nerd tool. So not for everyone. I think the modeling part is a lot easier. The rigging, rendering, particles, sculpting and animation is where things get complex, and all those capabilities are half ass, not world-class. So that seems like a strategic mistake on their part.
I recommend you get the trial at a time you can explore it and dive into it a bit before you decide. Itās not for everyone.
Another crazy option: Zbrush
Even deeper learning curve and more of a 3D sketching, zero dimensional control but powerful for those who master it. https://www.youtube.com/watch?v=Ixxx82ZsnLk
Tsplines in Fusion in my opinion is slow and limited of form creation, a lot more CAD friendly but itās a minivan, not a sports car. So it depends what you value more. Also I suspect stability might be worse than Modo, but Iām not sure.
I hope this helps,
G