I would say it depends the case, individual domainer (investment and buy/sell) or managing domains for a mid sized to big company?
When managing domains for a company - I think domains are not very expensive assets and leaders well integrated that (what? $10 for a .com?!) so I would say price is not the main driver. Of course paying >$200 for defensive domains hurts and I would not do that too much.
When speaking of vital (linked to brand hence company existence), critical (running services/api) and important (running minor services or intranet) domains, the
risk is the most important criteria and your boss would have bad nights and cold sweat returning by cycle every x months if they are not fully convinced/reassured that those assets are paranoidly monitored and taken care.
Then maintenance then cost maybe not in this order, but need balancing.
When being an individual domainer, I think costs matter more but often if you don't pay with money you pay with your time.
It also depends if your portfolio is full of easy or difficult TLDs.
For instance, you can deal with more registrars/resellers (10 or 20) if you deal only a few major gTLDs or nTLDs since they would have a proper public whois/rdap for retrieving domains informations. They also don't need local presence and have a "lifecycle" very common.
I would not spread each ccTLD in a local registrar (this is where it is almost always the cheapest price) ending up having hundreds of registrars but a total nightmare in managing.
If you want my personal checklist (not in order, depends what assets I will put here):
- Price
- Reputation of registrar (certification, no bad press) - different expectation for cheap or B2B registrar here
- Broad coverage of TLDs
- Provide a read only API
- Multiple payment methods:
- For a cheap registrar - can pay by card, multiple cards can be stored, auto renewal will charge on card, and if once card added if we can pay new purchase without OTP and card verification it's even better

- For a B2B registrar - can pay on receiving invoice (invoice sent to department company) and no need to top up
- Support (for B2B registrar)