I believe I am superbly qualified (if I say so myself) to discuss all things wood cutting related.
I am wood machinist by trade (think the guy that makes the bits that chair makers and cabinet makers put together) , have worked as a machinist, carpenter, selling power tools at M10 and I am now a trade instructor in the carpentry workshops in a big Qld prison.
Nobody tests the reliability of power tools like a bunch of unmotivated drug dealers, murderers, wife beaters and illiterate, violent thugs
First up.
The quality of the cut is related to a lot of things: speed at which you drop the saw on to the timber ( I'm constantly telling our workers that a drop saw is not a fucking axe, let the blade do the work) how sharp the blade is, how many teeth per inch the blade has (more is better for a fine cut but will make the saw work harder) what angle those teeth are ground at, what condition the saw bearings are in, how rigid the chassis of the saw is.
When selecting a saw more $$ is generally better.
Do not buy a compound mitre saw if you will not be doing compound cuts. The extra moving parts decrease the rigidity of the chassis and accuracy of the cut.
Same goes for a sliding mitre saw, cheap ones flex and are hopeless. You are better off buying a standard non compound mitre saw with a fairly large diameter blade .
I would think that to get a saw with a 50mm thickness cut and 300mm width that cuts well you would be spending big$$.
For the record.
We have had 6 of the latest model sliding compound Makita saws at work that have only lasted about 12 months. They have failed for one main reason:
In order to allow for the compound function the back fence of the saw has to slid out of the way of the saw motor when it tilts, this is accomplished by Makita making the fence out of cast aluminium. This is very brittle, one missed timed cut by a cak handed worked and the timber gets slammed back in to the fence and it breaks, end of saw. We have also had two fail at the gear box.
Bottom line:
Spend as much as you can
Stay away from compound saws unless you really need to cut compound angles
Speed the money and buy a nice fine tooth saw blade if you want to cut fine, cabinet grade cuts