Hi Capt:
I think the rule of thumb on machines is that bigger/heavier is always better?
Should be qualified a bit. You qualified your question a bit by stating that the mill purchase is a "want", not a need - so buy what you want.
DavidR8's advise is certainly correct - to a point. If you don't have power, space or machine moving abilities for a larger machine, then obviously bigger and heavier is not better, if you can't use it.
If space, power, weight are no issue for you - then a bigger machine is certainly more capable. This statement is still valid only up to a point. I have two manual mills:
- the smaller is an odd ball multi function tool room mill (called a "die sinker"). It is a very nice machine, extremely adaptable, but the movements / work envelop is pretty small (slightly smaller than the PM25 but 7x the weight).
- the larger is a regular knee mill, 10x48 table and has all the standard features / options that these were sold with - weight is ~#2700.
My larger mill is significantly easier to use than the small one, since the movements are a decent size - so the set ups are simpler. While I see it as substantial piece of metal - it really is NOT a "big" mill - it is about the smallest mill that Cinci made.
Yes, there is much to be gained. The PM30 will give you significantly more capability than the PM25. They are both small machines, but if your projects (with vise and spindle tooling) will fit in the work envelop - then you will be fine. Lots of good work has been done on PM25/30 sized machines.