+1 for Brad's comments regarding determining your market.
The reason that you're getting so much conflicting advice is that you haven't given us (or yourself, probably) enough analysis of your potential market to know what recommendation to make. The question of 1 sub being better than another seems to fall into the "extremely subjective" category, thus the plethora of responses that you've gotten on that front.
Until you can clarify the annoying details of plan, then I don't think that you should look at 1 box vs. another. Larger issues include cash flow, market potential, transportation and logistics, help/potential employees. Until you know where you can take this little venture you've started, you can't know what format of system to look to.
How many gigs do you think you personally could do per week/month? Lots of the system engineers on the lab do 4-7 events or more per week. Do you think you can endure this? Do you have the time or interest to do this? How much can you charge for each of these events?
Once you know that, then you can start to look at where you should take a potential system. If you plan on your sound company being you and a helper doing 1-4 events per month, then 200 pound cabs like TX8's would make a lot of sense. If you want to see how far you can take this little company, then things like outside financing (like a bank) is something that you should investigate. For many events, the sticker on the speaker and the mixer are the most important way to get your foot in the door, so you need those entry-level badges before many will listen to you. This is where you would get a bank loan. Nevertheless, getting serious like this requires some serious financial acumen to forecast things like transportation costs, equipment wear and depreciation, and other real business/accounting ideas and concerns.
In short, take some time to think this through; decide what your expectations are and realize that most of running a sustainable sound business is more about the business than about the sound.
Jon