Choice of film - like choice of camera - is a very personal thing.
With 'name brands' like Kodak, Agfa and Ilford you get what you pay for. High quality and consistency.
With cheaper brands this is not a given. Some are made under license by one of the above and some are made by other companies like ORWO. There aren't that many around making B&W these days, though.
How come the film is cheaper?
One thing they do is put in less silver - which can save the company a fortune. You still get useable negs but they don't provide quite the same degree of tonal gradation, resolving power and latitude. They also cut corners on quality control in that their acceptable limits are more relaxed. Quality can be a bit variable, as can film speed.
In everyday use most people don't notice these differences - but if you ever do anything critical or that pushes the technical limits, then you'll notice.
'Cheap' films are fine for learning and day to day photography. There is nothing wrong with them. If you are doing anything important, where you need to be 100% sure of what you are going to get, then use one of the top three.
You can see film as being a bit like cars. They will all get you from A to B in varying degrees of style and comfort - but if all you are looking for is something dirt cheap then you may end up with a second hand Trabant.
As for personal choice - well, it's just that: personal.
It's normally dictated by what you can get on with and whether you like the results or not.
I have known people who have extolled the virtues of most films and so I have tried them all. But the only film I have ever found I can use and that I like is Kodak. Ilford and Agfa (whatever I do) are always disasters.
Even so, I can only get on with certain Kodak films.
I'm rubbish with Panatomic-X or any T-max. The only two films that give me what I want are Tri-X and Plus-X.
It will, of course, be different for everyone else.
Just try them all and see which one you like.