transfer switch for a portable generator
I've got a question as to what type of switch to use for a portable generator hook up for residential use. I have a 7500 watt portable generator with a 12125watt surge capacity. In a previous home I had it hooked up to the main Square D panel with one of those lock out breakers made for the panel. I know some here don't like them but they are approved for code. So now I'm in a new house and no Squared D main and I want to legally hook up the genset. I'm not a big fan of the transfer switches with the set number of circuits that run off them (6-10). I'd prefer one of the switches that hooks into the main drop before the panel that allows the whole panel to be run from the genset. This way I can pick and choose which circuits I choose to power. One I had in mind is this one http://nooutage.com/7215.htm
I have a 200 amp service. I know I'd have to moniter what I am running so I wouldn't overload the generator and fry it. This way I could shut things down and heat up the hot water heater as needed or use other larger loads. My question is there any advantage or disadvantage of this type of switch vs the other self contained transfer switches? Also from the sparkys, It seems that the single switch would be less expensive to install since you wouldn't be hooking up all the sub circuits to it. Can anyone give me a ball park figure on what I'd pay to have it installed. I'd probably do the generator inlet run my self and have the wire there for the electrician to install. I already have the inlet box for outdoors hook up to the generator. Lastly, can anyone comment on why they don't like those lockout breakers that go in the Square D panels.
In advance, thanks for the great advice that you folks have always responded with over the years. You've saved me from doing some stupid things a few times.