Like with many things you can't say the Sennheisers are better because of x, y or z because there's a trade off and personal choice. Objectively speaking, the Sennheisers are an open back design so they come with the advantages of a more open and natural sound. As Phil said above too, they also help keep your ears cooler as air can circulate out of the cups. The open back design comes with a disadvantage though - they don't isolate you as much so outside noise will be heard more with open back vs closed back (like the Astros). The open / closed also applies to what you're listening to leaking out - open means more sound will leak for others to hear and closed are more isolating. I can't comment to newer A40's or A50's but way back when I bought mine, the PC360's used to review as one of, if not the, best gaming headsets available both in sound and quality and I can't imagine much has overtaken them unless you're talking silly money.
Subjectively, I only got to try the A40's in a shop for fit and comfort and I much preferred the PC360's though I do accept I have an unusually large head so maybe that was something to do with it. I didn't get to try the Astro's for sound when I tried them on so I can't spead directly to their sound. However, even compared to very good closed back headphones I own, I much prefer the open back sound. The open backs give a feeling of openess (duh!) so they're more like having speakers close to you than having the sound in your head. I also find the sound quality of the open back much more natural and less bass heavy that a lot of closed back suffer from. I also find I can listen to music on open back headphones a lot longer than closed - this isn't a physical comfort thing of actually wearing the headphones, it's almost like an ear strain.
I realise I probably sound like such an audiophile dick now though so I'm going to stop talking and go back to my 10 pairs of headphones 😆