I designed my own bench, customized to my ergonomics and the space I had to work with. I started with the principle that is should be very sturdy. That has payed off over and over again. The stresses you put on the bench when sizing or reforming brass, for example, are substantial and will bend the top to some degree.
Less bending is better. Accordingly, I used 6X6 cedar beams for the vertical pieces and 2X6 pine planks for the top, reinforced underneath with 2X4s. Everything is held together with carriage bolts, not nails. The height of the working surface was set so my forearms can rest comfortably on the work surface when standing. The whole thing is anchored against the wall in a corner of my basement.
The top is approx 5 feet wide by 2 feet deep. I have a large vise permanently bolted to the outer corner, with a LocknLoad powder measure stand next to that and an RCBS Rockchucker next to that. At the opposite end, I have a Lyman case trimmer permanently mounted. In between these fixtures, I have perhaps 2-1/2 feet of open space with some holes drilled for other devices which are used less frequently, e.g., cast bullet sizers and a Lee Loadall (shotshells).
I suppose you could buy a ready made bench kit, or buy someone else's design, but it seems more appropriate, if you have rudimentary carpentry skills and tools, to make your own, custom fit for you and the dimensions of your basement/garage/back porch. - CW