Important questions to consider
1- what is the junk all over the Praxis...just dust or something that isnt easily removed?
2- since its used, does the Praxis crank include the necessary bottom bracket for your bike or would that be additional?
3- is 52/36 what you need and what you would get on the 105? If you would buy a different combo new, then that should help answer your question.
4- how much $ is the 105 crank? Online they are $110-130. So I would guess $140 or so in store. That puts the Praxis at $200. The Praxis is old- not sure how old, but rings dont look like that anymore. They could be in great condition and basically new, but just be aware you arent buying a used current model for $200.


I would find out what the used crank is comparable to new for Praxis. Is it comparable to Zayante or Alba? A new Alba with bottom bracket is only $210 or so, just for reference. From what you have said and the pic, I think the Praxis is overpriced.
With that said...
I find the current Shimano cranks to be aesthetic abominations. Its like it was designed by a group of 4 year olds and the preschool teacher is telling everyone the crank is lighter and stiffer to make the kids feel good.
The Praxis is clean, 5 arm, and has a more elegant arm shape.


Do some research on the Praxis for sure. BB included? Weight? What would a new Praxis at the same level cost instead?