Apart from outstanding qualities you get with a Professional Tape Recorder, one of (the many) reasons is the sense of getting something which you could not dream of (which is why I now own 6 of them :)). Who can afford a tape recorder for the price of a car? And the feel - "that this machine is something" ...
I even do not know where to start here... You just have to buy any PRO machine in a good condition - and you will understand :-))) Ok... They are Bigger (with the exception of consumer sized TASCAM 32 and 34, which are often used as home Hi-Fi). They are Heavier. They have very solid and smooth tape transport.
Some of professional machines are cabinet mounted and have cart wheels to move around if needed, which is a convenient thing, considering they can weigh from 22-50 kg (any good R2R recorder, including the consumer types, weighs not less than 17-20 kg). If the stand has rollers, it very much improves and eases handling. Such a machine converts your men's cave into a sophisticated living space containing a sophisticated piece of machinery, which is also an element of interior design. You immediately are a guy who is in a different league. And even better if you actually use it as your main music playback device - instead of (no offence) CD, MP3 or other digital device.
Professional Machines use only two tracks in a stereo mode on 1/4 inch (6.3mm) tape. They do not have Auto reverse function. You play the tape and then you need to rewind it. Of course the recording quality of machine, which is properly maintained and calibrated according to tape you are using, is out of this world. To achieve this High End result, the recorder must be calibrated and serviced and also other than a consumer tape should be used. If you don't - it will still record superbly, but you won't get a maximum performance these machines are capable of. A good thing is that you calibrate it only once, and then use always the same type of tape. There are machines who can be calibrated for several types of tape. You do not do this for consumer recorders. These you just plug and play.
Of course you should not forget to also clean their heads from time to time.
In the beginning of my article What Reel to Reel Recorder to Choose I mentioned 1/2 inch tape machines that are using a tape, which is 2 times wider than conventional 1/4 inch tape. If you want to use your professional machine as a home recorder in consumer mode, you need a wider tape (besides improved quality - it is also easier to handle). Using this tape you can record 4 tracks and have "2-sides" of tape containing stereo recording.
Most Popular Professional Hi-Fi machines
The all time winner in the professional arena is, of course, the iconic Studer. Swiss precision engineering. And precision is the key for the tape recorder. You can change, tune, upgrade the electronics of the audio tract of the recorder - whatever you like. But little you can do with the "clockwork" - the tape transport. Tape transport makes 90% of the sound quality of the recorder. Nowadays tape transports also can be improved (tuned) with today's technological means making them even better than they were new back in 70-ies and 80-ies. But again, I will not talk about this - you will do it only if you will become seriously addicted, in which case at the end of the day your tape recorder will turn out to cost more than your car.
List of popular models:
STUDER: A-80, A-807, A-810, A-812, A-820
OTARI: MX-5050, MX-55, MTR-10, MTR12
SONY: APR-5000 series
MCI: JH series (later purchased by Sony and seized to exist)
AMPEX: ATR-100 series, ATR-700, ATR-800
TASCAM: 32, 34B, 42, 52, ATR-60-2, BR-20
Apart from these there are more strange and very interesting beasts. Just to name a few:
NAGRA. A rare brand - more known by their portable recorders used by reporters.
MECHLABOR. Hungarian, but very, very good. Not known widely only because of the Iron Curtain.
FOSTEX. Not favoured among professionals - more used at home studios. But it has some really interesting consumer-usable models like A-8 LRL, E-2, A-4, A-4.
The world of Reel tape recorders is as interesting and versatile as for classic cars. Considering that you read this, first of all, it is because you think it's cool. Which it is! And if you find a friend in his 50-ies, who is familiar with electronics, he can open the whole new world of Analogue tape recorders for you.