Anything Worth Doing Is Worth Doing Right!
I,ve been reloading off and on for 30 years and have built many benches and storage areas over the years due to relocation. I see that this thread is dated however, if you've yet to begin, or for others not yet started, here is my experience.
PLAN FOR GROWTH! If you can... build your bench twice as large as you've planned and build lots and lots of shelves. Shelves will keep your work area workable and allow you easy viewing and access to all of your components and reloading data. A plastic portable table is NOT the way to go. It is BEST if your bench does not flex, bend or move. It will affected how your press performs. Try to mount the bench to the wall or build a continuous shelf spanning all four legs and weight it down with components or anything to keep the bench from moving.
I built an eight foot long bench and added three presses in a couple of years. This year I built a second loading bench, free stannding in the middle of the room, that is 4' x 6' on 4" x 6" legs. It has a 4' x 6' shelf 12" off the floor and it is full of heavy stuff... it's not moving! A forth press was added.
All this work area does not include a 3' x 3' top mounted to an old chest-of-drawers for gun cleaning and maintence.
And lots and lots and lots of shelves.
If you don't plan for growth while building your bench some day sooner than you think you will say to yourself... "I should have made this bigger!" Can you tell I love reloading and shooting!
Hope this helps someone during the planning stage.