heh i wouldn't call myself an expert on anything, the only thing i look at is if it makes sense from a physics stand point
it's hard to keep focus with all the marketing material and hype surrounding a product but generally speaking if you take a step back and look at it from a pure physics point of view, you often can overlook the hype and get to the meat of the claims.
as far as comparing delta vs sanyo danki... it's like comparing a Mercedes vs BMW
quality wise, they are both very strong OEM of fans and comparison can only be made on a model to model basis. both have EXCELLENT fans and both are "generally" more then overkill for the purpose of consumer grade computer cooling.
things to keep in mind when selecting fans are static pressure, CFM, and dba rating of the fan. many people SAY they don't care about noise and just want the best cooling till they had to live with their choices
the key to selecting the best fan is to balance the amount of airflow needed to achieve the desired result while keeping the decibel at its lowest possible level. generally speaking anything above 2000RPM would be "too loud" for consumer/home use purposes.
alot of people would suggest you get a much stronger fan then you need then dial it down by under-volting it. the problem with that is when it's undervolted, it doesn't perform any better then the weaker/quieter fan in the 1st place
so there is really no reason to buy a $60 fan just to under-volt it to perform like a $12 fan
when evaluating what fans to get, you must 1st realize there are 2 distinctly different focus in fans. the 1st is to optimize static pressure so the fan can overcome airflow resistance caused by air filter/radiator/grill/other objects blocking airflow/etc... for strong static pressure, you generally want fans with alot of fan blade surface area so it's able to push against more air at lower speed. if you look at the scythe GT's
you will notice that their fan blades are curved and elongated to maximize the surface area of the blades themselves.
if you look at the corsair SP fans
you will notice that they blades themselves are much wider then typical fans so there is more surface area pressing against the air and moving it.
both of these designs increase surface area so that more energy of the fan motor is transferred to the air that it's pushing against. (or same energy but at lower RPM)
there are other fans that use a different method all together. they use ALOT more blades (11 blades instead of 7 or 9) to increase the surface area of the fanblades
so the energy transfer from the motor to the air it's pushing is more effective.
other concerns about static pressure generally has to do with angle of attack of the blades themselves (how it's curved) and static fins/grill that focuses the airflow after it's been pushed by the fan blades. here are some examples
as to what is the "best" there really isn't a "best" per se because it comes down to the fan design and manufacturing quality. GENERALLY speaking the scythe GT's are consider the favorites at OCN because they've proven themselves over the years. that's not to say that it's superior to a Delta, just that it's impressed more people on OCN over the years with it's reliable performance balanced with its acceptable acoustic signature.
on the flip side of the fan focus is the CFM optimized fans.(exhaust fans) i rarely pay much attention to these types of fans because pretty much any fan can fill this role as long as it's quiet
they just need to remove enough air from the case so there is no "back pressure" built up that allows for hot spots to develop within the case itself. personally i don't use an exhaust fan on my machine since my case (FT02) is as optimized for alr flow as a case can be anyway
there is no back pressure or hot spot that can develop in that case
i suppose i CAN put an exhaust fan on it, but IMO its benefit is negligible.
so... when asking advice on what fans to use, you generally want to narrow the scope of the question 1st so we can offer better advice as to what fan may best fit your needs.