Not in the USA so not familiar with local grasses or georgaphy.
However the best cut (not a good describer ) so I will say the cleanest cut will come from a deck where the blades have the biggest overlap
So for a 42 " deck, if the blades are 21" each, they will leave an uncut strip between them in a very short time .
A 22" blade will only ever leave an uncut strip when doing tight right turns .
Now the finest cut will come from a timed deck where the blades are set at right angles to each other .
Very few mower companies offer these types of decks because they add to the costs as 2 x 33" blades cost more than 2 x 21.125" blades .
I like the articulated mowers with the full mulch or rear discharge decks .
However they do not suit a lot of people as their decks will be overwhelmed if you let the grass grow too long between cuts .
In the USA Husqvarna & Stiga do this style of mower ( only Husqvarna mower I ever recommend )
For better answers the boys will need to know a bit more about your mowing habits , frequency , time of day , bag , mulch, throw, leaves etc .