Oxford Espress

Definitely superior to the Oxford Tube. Fewer tourists and groups so quieter, also cleaner and with a nicer interior. It also doesn’t make that irritating stop in the middle of the countryside, and Baker Street is much more convenient than Marble Arch for Bloomsbury/​British Library. It has all the same stuff otherwise: power sockets, wifi, reclining seats.
My only bugbear other than the inevitable unreliability of traffic is that twice I’ve been passed over at Baker Street because the coach filled up. A rare occurrence but a pretty galling one in bad weather!

The Oxford Espress competes with the Oxford Tube in providing a coach service from Oxford to London. Their service is largely similar to the Tube, stopping at the same stops (except for an extra stop made by the Tube, where almost no-​one ever gets off). They also offer Wifi and in fact, used to give free breakfast on services before 6.30am. The frequency of their services does decrease in the evening, so if you’re coming back very late at night, it may be better to buy a Tube return. Note that if you leave Oxford after 3pm and are returning the next day, you can buy a cheaper return than normal.

I commute by coach to London nearly every day. If you want a (slightly) faster service, the Espress is the way to go. There aren’t as many seats (no double deckers), but they don’t stop at Junction 6, drive a little bit faster, and only stop when someone has buzzed (good for those traveling from the town centre).
UPDATE: I now have a different job and don’t use the buses as often. The competitor to the Espress, the Oxford Tube, bought all new buses a couple of years ago, so the competition is intense. Between the two companies, this route is apparently one of the busiest bus routes in Europe.

Much better than the Oxford Tube.
Drivers are friendly and helpful, but I’m afraid this service is just as uncomfortable. It is just a little bit cheaper than the train (without a railcard).
Wifi works better than the Oxford Tube, but not very reliable.
It is very slow in peak hours, but reasonably quick in quiet times.