The best controller depends on your needs. If a simple atmega based board fits your needs, just use that. No sense in using a sledge to swat a fly. As for servos, there are some servo which can be driven with a step/dir signal just like stepper motor drivers, so your control board can treat them the same. Making your own arduino controller to control a servo using step/dir isn't worth it unless you're very familiar with control loops and tuning them.
Also, servos aren't necessarily quieter, I'm not sure what's convinced you of that. The noise people typically associate with steppers is more an artefact of the stepper drivers commonly used in 3D printers. If you want servos the cheapest option I can think of is a mechaduino, which is a NEMA17 fitted with an encoder and arduino to provide closed loop feedback, this can be run with a step/dir signal from the control board like a regular stepper.
The O-Drive control board is another option, it lets you use a regular RC brushless motor, mount an encoder to it and drive it like a servo. This is a bit more pricey but the motors can be a lot more powerful and a lot faster for the same form factor, but a 3D printer won't really be going fast enough to take advantage of that. On the flip side brushless RC motors have pretty weak holding torque, not that it really matters for a 3D printer.
Final suggestion; don't make it that big. Even industrial machines don't really go that big. Even with a heated chamber you'll get distortion and warping. Not to mention with a build chamber that size you're looking at print times upwards of a week or even more, the chances of nothing going wrong during such a long print are small. What are you even going to print that large? Plastic parts, especially 3D prints, at that size are probably too weak to be useful.
sorry for all the weird line breaks, my post keeps getting formatted to remove new lines/paragraph breaks for some reason.