Epson Ensemble HD 720 compared to the Ensemble HD 6100
Front end price vs. Long term cost of operation and higher resolution, summarizes the difference between these two options. As noted in the similar page on the 6100 version, you save $1300 upfront with the 720, but, over a number of years, you can recoup a lot of that with operational savings on the 6100 thanks to the longer life lamp. Think this way. By the time you get to 8000 total hours, you will have just finished up your second lamp with the 6100, while you will be within 500 hours of using up your 5th lamp on the Ensemble HD 720. At $350 a lamp - when you buy the 5th one for your 720 - you will have spent $1400. When you buy your 3rd for the 6100 version, you will have spent $700. That's a cool $700 savings. By 10,000 hours, you'll have bought 6 lamps vs. 2 (but you'll have used half of the 6100's lamp by then).
In other words, for a moderately heavy user - 24 hours a week - the lamp savings will have offset the entire price difference in 8 or 9 years. For folks running 40 hours, figure about 5 years and change.
So, if you are planning on buying a keeping an Ensemble for a very long time, and the upfront price difference isn't a big deal, the 6100 may be the more attractive version, with slightly better picture quality, and higher resolution.
Epson Ensemble HD 720 compared to the Ensemble HD 6500UB
Enthusiasts will certainly prefer to own the 6500UB version of the Ensemble HD, as it is perhaps the best overall projector anywhere near its price point, and comparable to many far more expensive projectors. The same long term cost savings that I covered above, apply when comparing the Ensemble HD 720 to the 6500UB version. For your $2200 difference, you get not only higher resolution, but a truly superior picture thanks to the outstanding black level performance of the 6500 UB projector, as well as the long term savings of a longer life lamp.
The interesting thing, though, about the pricing differences, is that a stand-alone 6500UB sells for about $1600 - $1800 more than a stand alone 720 projector.
This means that you can really start out (if the budget is tight) with the Ensemble HD 720, and, perhaps 6 months or a year from now, upgrade the projector. I figure that by 12/09, the high price of the 6500UB online will be no more than $2500, and probably at least a couple hundred dollars less. As mentioned in the Ensemble HD 6500UB page, You could then replace the Epson 720 projector with the 6500UB. You are shelling out, perhaps $2500 (let's figure high) for that projector, but your used Home Cinema 720, should command at least $400, and probably $500 - $600. Using the $500 number:
Ensemble HD 720, with later upgrade to 6500UB: $4699 + $2500 = $7199 - $400 (for the sale of the 720 projector) = $6799. That compares with $6899 if you just start with the Ensemble HD 6500UB. In other words, you can start "on the cheap", but end up the same place, without it costing you more in the long run.
I think this is a great approach for a lot of first time home theater folks. The Ensemble HD 720 is affordable, but many people "get the bug" and become enthusiasts, and ultimately go out looking to improve their setups. This is a great way to accomplish that. Technically down the road (dare I say it), you could even drop in a different brand of projector - as long as it fits inside the cradle, has the necessary lens throw and shift to fill your screen properly, and doesn't run hotter than the Epson projector. Note: DLP models typically run hotter, as they use higher wattage lamps, however in a couple of years it's likely that most projectors coming out will have LED light sources (cooler running), rather than the conventional UHP lamps.