for me price per gb ram per month because memory is always my bottleneck

In no particular order:

• Price (if looking to host something low value)
• Price/performance (if longer-term)
• Details of Fair Usage Policy
• Bandwidth limits
• Overlimit pricing
• Location - proximity
• Location - creepiness of government / jurisdiction
• Reputation of the company - are they scummy? Do they oversell? Is their datacenter about to get yeeted? (cough Dedipath cough)
• Are they bullshitting me with RAID 100000 PURE SSD STORAGE!!!!!

In fact, I actually prefer HDD storage for most of my servers: for most websites, your bandwidth will be a bigger limitation than your data access speed.

Your skill level vs there support knowledge base and they type of support you may need.

Which benchmarks should one compare between providers?

I prefer VPS with good price/performance.

Has to be KVM based. Then I look at shared / dedicated CPU cores and IO disk speed.

I like Hetzner. Very high price/performance, pretty easy, no complaints.