That's a very backwards way of thinking about it in my opinion. The question you should be asking is "What size wood am I cutting with it?", then decide the bar size.
If you are falling a lot of trees 3 feet and over, a 28" bar might be just the ticket. Myself, I normally run a 20" bar on a 066. I have larger bars on hand too though, that I'll attacth if I think I'm gonna be in big stuff any particualr day. It would be silly to go at stuff that's 99% bellow 30 inches in diameter (that's already down), or falling trees below 20 inches, with anything more than 20 inches. It's just extra annoyance with the bar being overly long and unmenouvarable, and it's more likely to get in the dirt.
I've falled some pretty big trees with a 20" by the way. A 046 benifits very much from it power in hardwood even with a 20 inch bar as oposed to a weaker saw.
Brands? I'd say oragon or stihl brand, but there's lots of good brands out there.