What size of log can your processor take? What species of tree are you likely to be cutting? Can you file and or grind chains to keep them at optimum?
Bigger engine saw will do what a smaller engine saw can do, but the smaller can never fully do what the larger saw can do- plus it is bolted to a frame, so no need to worry about and power to weight or carry weight arguments.
If it were me and I was in a permanent yard bringing logs to the processor- I would be running an electric saw, but given your choices currently I would be using the 064, then if need must or the logs are small enough to warrant it, the 044 as a second choice.
At the end of the day they are tools, tools wear out through use, but they are designed to be used not polished and looked at.
If we all go into a panic about preserving older saws and not using them for fear of not being able to buy a new part at the dealers on any given day you choose to walk in and ask for it- the World will be full of spit polished older saws with no collector value because they are not rare.
Use what you have, maintain it and take care of it as you do now and it will process many tonnes of firewood for you.
