VLSD: doesn't work when you need it. works only 5/8th of the time. Mine's fail once awhile.
Welded: Whatever Taka said in that link i posted.

 

vlsd's work better when the fluid is warmed up

 

it works whenever it feels like it.

 

vlsd is unpredictable, welded is awesome, but does get annoying for dd, ive had mine welded since feb. and since then ive done tons of drifting, also drove to louisiana and back, chicago and back, and all over florida, havent had any lock up problems. but im looking to save for a 2 way now

 

S15 HLSD it is the best of both worlds.

 

my vlsd works fine make sure the fluid is good, and it doesnt have jillion miles on it.

 

yeah haha, and obviously doesn't give close to 50/50 power even when it does.

"Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. They do not stand up well to abuse, particularly any sustained load which overheats the silicone results in sudden permanent loss of the LSD effect. They do have the virtue of failing gracefully, reverting to semi-open diff behaviour, without the graunching of metal particles / fragmented clutches. Typically a viscous-differential that has covered 60,000 miles or more will be functioning largely as an open differential. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the diff. This is not serviceable and when the diff's behavior deteriorates, the VLSD center is replaced."