The chronic complaint heard here on Sailnet is that the Volvo parts are astronomically priced.
Yanmar makes a good engine, with reasonable but nevertheless "marine" prices for spares.
I would suggest that you compare the value of the Betamarine engines (marinized Kubato). You can get spare parts for them very cheaply at the tractor shops. The BD722 is a nice engine, as is the BD-902.
Many re-powering threads here on Sailnet. Here's one where a few of us discussed different options and their advantages: Repowering
To save you some time, here are my comments about the Beta engine from that thread:
Originally Posted by JohnRPollard
I got a price of $6800 for the BD722 when I inquired with Beta a month or two ago. That's not a whole lot less than your Yanmar 3YM20 price. But you'd have to study the specs to see what the respective prices include. For instance, the Beta price includes a new transmission, motor mounts, control panel, a PTO, etc.
Off the top of my head, some differences that I recall are that the Betas have built-in oil change pumps, shallow sump options, and glow plugs. Also, the Beta raw water pump is cam driven off the engine, so there is only a single belt (for the alternator and fresh water pump).
Another consideration is that the Betas are based on the ubiquitous Kubota tractor engines, so the replacement parts tend to be cheaper and more readily available than Yanmar.