Personally, I'm of the getting the best battery possible club. From my 21 years experience on the road, there is nothing worse than having dead, or low batteries. So after trying most all makes from generic on up, I have settled on using the Trojan size 31 1000cca batteries (2) for starting since they are close to the 2 8D's I replaced them with. Presently, my batts are just over 5 years old and still starts fine, even after sitting for a few
Trojan is no longer making starting batteries. Strictly deep cycle according to AAA Battery here in town.
Sure, I would like the best, but a single Lifeline 8D battery costs about the same as 8 GC2 batteries and the amperage is double on the GC2s. Yes, there is more chance of battery trouble with eight instead of two batteries, but I can live with that for half the cost.
If I was fulltiming, the best batteries might make sense, but I am not. My project has cost a good 1/3 more than I had planned so I will have to get by with less epxensive batteries for now. (I had created a very detailed budget when I started, but I way underestimated some costs.)