I have access to both a MFC-7840W and a MFC-9325CW.
Well, there's your problem.
In my experience, Brother HL-series black lasers get questionable after about 150,000 duplexed pages due to roller wear, but other than that that they're solid. I don't much care for their MFCs though; besides the build becoming awkward due to integrating a scanner, the fax capability is usually about as useful as a USB pet rock, and the driver software they come with is frankly crap -- doubly so if you use the network-based interfaces.
As for personal use, my venerable HP LaserJet 4L continues to serve, and its no-corona-discharge-wire design is a nice touch. Old enough that it could probably use some new rollers to reduce misfeeds, but it still works.