I use both trays and a Nikor SS tank for 4x5". The Nikor tank can handle up to 12 sheets and uses 1200ml of solution, so if I have six or more sheets with the same development time, I tend to use the tank. If I have a small mixed batch of sheets with different development times in the same developer, then I use trays.

If you have a darkroom, you'll have trays anyway, so you might as well start with what you have, and then add a tank when you want.

Tanklines and hangars are a good method if you have a lot of film to develop on a regular basis, prefer a replenishable developer, and have room for the tankline.