There's a lot to consider when comparing the Littco and EQT offerings. First and foremost, both Ed from EQT and Dan from Littco seem to be top notch guys to do business with. I look forward to their contributions later in this thread.
Price
The L450 and EQT are very close. My L450 with Turbosmart DV, Largebore muffler delete, shipping, and $35 bank transfer fee was about $2,150. Skip the Turbosmart and that's about $1900 all in (with a DV and Actuator included).
EQT is $1845 shipped, or $2045 if you add the muffler delete and chargepipes, which you should do at this level of airflow. The stock pipes work well up to IS38 levels, but become a restriction above that. One of the EQT guys can correct me if i'm wrong, but i don't believe this includes a DV or actuator.
The L500 with the big muffler delete, shipping, and wire fee runs a little over $2600, about $700 more than the L450, so there's definitely a real increase in price to move to the bigger unit.
Power Capacity
This gets interesting. There is very limited independent data on this, so i've had to piece this together as best i can.
EQT has been very open about the fact that his dyno reads higher than average. Littco on the other hand uses a dyno that reads considerably lower than average, and publishes his numbers on Euro 99 RON (slightly better than US 93 octane).
One could look at the 500whp EQT made on their dyno with E30, and the 395whp the L450 made on their dyno, and conclude there is a giant power gap between the two turbos. In reality, it's somewhere in the neighborhood of 30hp.
The EQT flows in between the L450 and L500. It uses a 53mm compressor wheel, which basically splits the difference between the L450 and L500.
EQT runs a 54mm SL2 turbine, which is 2mm larger than the L450 and identical to the L500.
On the hot side, the EQT and L500 are extremely close, however the L500 does use a slightly larger compressor.
Everything equal, the EQT will most definitely make more power than the L450, but should come up a bit short of the L500.
Response
You can't cheat physics. Turbo design has come a long way, and we can now build turbos that flow pretty well and respond pretty well, but it should come as common sense that generally speaking the more air you move, the longer it takes to get it moving.
This is dictated more by the hot side than the cold side. The L450's primary design objective was to create a turbo that would respond as fast as possible while still flowing enough to hold good power to redline.
This is a big part of why the L450 uses the stock shaft and a 2mm smaller turbine wheel, but only a 1mm smaller compressor wheel (vs EQT). Not only is the shaft itself lighter than the TD06 used in the EQT and L500, but it allows the use of wheels that are also capable of faster response.
Because the EQT is running a bigger hot side relative to the compressor, it will be a slightly more efficient turbo, especially at high boost levels. This helps control temperature and is particularly beneficial on pump gas. The trade off for that slight increase in efficiency is a slight increase in lag.
Response will be the opposite of flow. The L450 should spool earlier and quicker than the EQT, which should very slightly beat out the L500 (again, the hot sides are nearly identical).
Reliability
It's far too early to have much real world data on this. Ed did have one issue with a unit that was not properly clearanced at the factory, and the customer had a new turbo on his doorstep 2 days later, so he went above and beyond to resolve that issue as quickly as possible and work with the supplier to ensure it would not happen again. One consideration is that Littco builds all of their turbos in house. Dan is the guy physically building the turbos. EQT uses a very reputable supplier building to his specs.
The L450 uses the stock shaft, which is a known failure point on IS38s. Dan has tested this extensively and concluded that the shaft failure is not inherent of a weak shaft, but the result of other problems (bearing issues, the wheel touching the housing, or the TCU tune slamming the throttle shut at full boost and creating a pressure surge that over-stresses the shaft). His conclusion is that when the other issues are addressed, the shaft is sufficient.
The Turbosmart DV is more reliable at high boost levels, and is also much faster to react to throttle closure than the stock DV. The faster reaction reduces stress on the shaft during throttle closure. That's the only reason i added the Turbosmart DV to my purchase.
The TD06 core used in the EQT & L500 is a stronger unit than the L450.
Both companies use their own thrust bearing designs, both of which are much more durable than stock.
Value
I have to give this to EQT. You get the beefy TD06 core and higher power capacity with the EQT, for about the same cost as the L450. The EQT is at the L450 price point, but in every way it's closer to the L500.
For me, the decision came down to some of my previous experience and what my goals are for the car. I wanted the fastest responding turbo that still had the capacity to meet my goals.
I used to DD a car with a Boss 700 equivalent. It was fast but the response made it miserable to live with in the real world. My goal for this setup is to have a fast reacting turbo that can make 420-430wtq (i'm at 434wtq now with the IS38, and i feel that is the reasonable limit for tractable power on a GTI) and hold it deep enough into the RPM range to pump out well into the 4xx whp range on reasonable, reliable boost...instead of the 399whp i'm making with the IS38 on time-bomb boost.
An IS38 isn't huge by any means, but it is a significant step up from an IS20. The difference between the IS20 and IS38 is 2.7mm on the compressor and 0.6mm on the turbine. The difference between the IS38 and the L450 is 6.8mm on the compressor and 4.6mm on the turbine. This is a sizable upgrade, even more so for the EQT and L500.
Actual airflow and power capacity compared to the Boss kits remains to be seen, but the L450 has a bigger compressor than a Boss 500 (with a smaller turbine). The EQT is very close to the Boss 600 in wheel size, and the L500 matches it.
The SL2 turbine on the EQT will add a bit of lag compared to the L450, but it will pay you back for that lag with increased efficiency and more support for the additional compressor flow. The L450 should spool sooner and respond faster, but it's not going to hang with the EQT out the back door, which in turn should come up a bit short of the L500.
All have wheels and housings spec'd out by their manufacturers for the application, but the application and the approach are a bit different from the L450 to the EQT and L500.
Time will tell, but i don't think there's a wrong choice if they are used within their intended design parameters / boost levels.
