I would love to know this as well--great question! Overwhelming to pick.

I have had a direct vent Majestic running for 12 years. I have found Majestic is constantly being bought and sold and replacement parts are very expensive. Recently quoted $55.00 CDN for a ten buck thermocouple. $550.00 for a replacement glass. I had gone through 3 fan bearings in 6 years and finally gave up replacing them at $225.00 each kit, had to buy an entire kit with parts I don't need because can't source the bearing alone.

I do not recommend Majestic. I do recommend that when you think you have made your choice, call a dealer and start asking about the cost of replacement parts. As well if the unit is fan driven check to see if the motor and bearing is
Insulated, of not keep shopping.
Many companies appear to be building units that can not be retrofitted with FitsAll type replacement parts. That $55.00 thermocouple was the only one that would thread into the fitting where a $10.00 thermocouple would have been fine. As well some companies technical specs limit other aftermarket parts being retrofitted.