Anyway, i say LLLL.nets are way better. Mainly because they have better chances of finding endusers. They're millions of companies out there with names that can use a LLLL as an acronym, not so with LLLLL. With 5L names you're just praying some funky startup like flikr or something approaches you for your name. And you know what, they dont need your 5L.
Dangit...had long response but browser crashed while viewing some other crap page.
Basically you just have to view Alexa top 500 and point out the LLLL.net's ...you won't find one. However you will find MANY 5L's or higher BRANDABLES.
Name me one company that's successful using a LLLL.net.
If a company startup has $xxx,xxx or higher startup budget...they are going to look for dot com and brandable a lot more than some acronym in a secondary TLD.
Monetizing the LLLL.net vs the LLLL.com is vastly different. The dot com will earn as parked while the .net equivelant is going to earn peanuts in comparison.
If you are going to like LLLL.net's that's fine but don't create a dillusion that LLLL.com's are less attractive. They are MORE attractive and for obvious reason. The only problem with 5L's is the combinations are vast and making sure your portfolio has quality brandables is very important. The criteria for what makes a good 5L brandable is subjective but I believe my portfolio is an example of an overall good quality set.
I believe a 5L brandable needs to be easily pronouncable and not a stretch to say it. The brandable shouldn't sound too much like a real word because that will only encourage typo's. Witza.com is perfect example imho. The radio test is a real litmus for brandables.
Lastly...you say that there are millions of companies that can use a LLLL.net and boy...that's a real stretch of the imagination for me. For one most companies do not use 4 words as a company name. For another they would want the dot com acronym. Lastly they would probably opt instead to have a shorter version that's NOT an acronym. Companies need to BRAND...and acronyms don't normally do that. (IBM maybe the exception).
I see this:
Apex Industrial Widget Company
and I don't see this as their url:
AIWC.net
I see this:
ApexWidget.com
ApexIndustrial.com
ApexIndistrialWidget.com
Maybe that's just me though.
And I just realized for SEO...the acronym is a crapper. You want a name that's going to be indexed properly. Any SEO expert will advise the company of this.