You're asking the same question that a lot of newbies ask. I asked the same thing myself. Then I went straight into flatbeds and did just fine. I'm only 5'10" 185# so not a big guy at all. As a matter of fact, I see more "big" guys pulling vans than flats.
Everyone will be different and, IMO, there is no reason to start with vans and move on to flatbeds. I'll agree with csramsey, they do not pull the same and they definitely do not back the same (if the flatbed is a spread axle as most are).
If flats are where your interest lies, go with a good company with a reputable training program (ie: Maverick, TMC). Then you won't have to worry so much about securing the load while your honing your driving skills. They will make sure you have a good grasp on the securement practices before they ever put you behind the wheel. The work is not that hard. I sound like a broken record, but I equate it to a halfway decent 20 minute gym workout.
The list of 10 companies is a good start. Personally, I would take it a step further and make a standard sheet with questions and print several copies. Things to ask (pay, hometime, regions, running lanes, benefits, etc...). You can find a very good list of questions here
http://www.newbiedriver.com/articles...ons_To_Ask.htm and then add to it. Call on 50 or so companies and ask the same questions, fill in the blanks and take notes. Then you start narrowing it down until you have a handful of carriers and make your choice from there. Find the best fit for you as far as what you're looking for regardless of whether they're flatbed, van or reefer.
Just my 2 cents... Good luck!