Bang for the buck is relative when you consider life expectancy vs labor cost to replace, etc. There is also the question of header size, as there is usually a $20-$40 per panel premium if you want 2 inch headers only really needed on banks of more than about 8-10 4ft wide panels. Another thing to be ware of is the warranty on panels, many warranties only cover installations by their licensed dealers, some major panels are available to the DIY market mostly through private label programs (Auqatherm through Elm Distributing, and Techno Solis through Solar Direct), private label panels are covered through the private label company so if buying from Solar Direct you would have to deal with them on warranty issues, not Techno Solis). There are a couple of other common gotcha's on warranties in the solar panel market, first none cover freight, and some offer a prorated deal where after X years all it means is the ability to buy a replacement panel at 1/2 of suggest retail price (which is all too close to every day discount price available online)
Regardless there is no one right solar panel, it partly depends on your climate, type of installation, etc. For example a flat rigid panel like the Techno Solis panels I have may perform better when installed at less than ideal angles and when there is wind as opposed the rippled tube style that AquaTherm made popular which may provide more area for solar absorption if mounted facing due south with little wind. By contrast the rigid Techno Solis panels may suffer more from expansion stress if partly shaded, which is not a problem in my location until late in the day when the sun is going down.\
Ike
p.s. I bought mine from poolheatpumps.com and was very happy with the transaction even though they did take 3 weeks to arrive, after getting them home and unloaded I found I was missing a fitting from one of the pre bagged panel kits (later I found one of the other panel kits was over one on a different fitting), I emailed my rep at poolheatpumps.com and they sent me a replacement kit, no questions asked. Price was also cheaper buying my Techno Solis panels from them with 2 inch headers than buying the rebranded 1.5 inch headers would have been from Solar Direct (big savings were on freight price)