I voted Pioneer cause that's what I've always used and liked. Never let me or anyone I know down.
Eclipse makes good stuff, but I don't think they'll ever live down the "E-skip" era that plagues them. That and a lot of people are having some pretty bad problems with turn on/off pop with last years offerings (specifically the 8443).
Kenwood ***** ass, plain and simple. Had one of their HU's break 5 times in 6 months....stupid POS
Eclipse has long since fixed the skipping problem, and the pop seems to be pretty much isolated to the 8443. Are those issues worse than Alpine's weak pre outs that they finally did something about in their '04 decks? There were countless posts from people on several forums complaining about the "weak sub out" on their alpines since I started on the forums in 01. Testing of some decks by forum members confirmed it. Alpine finally fixed the problem in this year's decks, and now their pre outs seem to be as strong as advertised.
I have used Eclipse decks for 10 years. I had one minor issue. My best friend ran an Alpine 7863. It crapped out 6 months later. Circuit City replaced it, and THAT 7863 crapped out 6 months later.
My point is, over the course of time, any manufacturer can have issues. The local shop has sold Eclipse since '92 or so. They stuck with Eclipse when they had the skipping issues, and since then(and before), they have had excellent results with Eclipse. Eclipse makes excellent sounding decks, and until I bought my RF 8250, Eclipse had made the best sounding decks I had used(having also used pioneer, kenwood, alpine, and clarion).
If Eclipse is not as popular, I can think of a few reasons why:
Their decks are not as flashy as many others
Their decks are not wh0red out everywhere like most other decks(you can find alpine, clarion, pioneer just about everywhere....authorized shops or not).
Eclipse has not been around quite as long as Alpine, Pioneer, Clarion, etc.