A very good question :thumbsup:, however it's one that we will never get a definitave answer to, there is almost certainly not a black & white answer.
So to declare my position. I have been a GTC / Cobb customer since quite early on, and have no experience of ECUTek. Here are my random thoughts on the question.
In the early days it was an easy choice to go with Cobb, although ECUTek had a lot of experience, they were very new to the R35 GT-R and there was no real data available, wheras the Cobb AP was well established in the US, with a large and growing customer base, with plenty of data to back up the gains.
Add to that the great convenience of doing the firmware upgrade yourself, data logging and tuning via email, and the ability to load and try different maps, or go back to standard and it was a very easy decision which way to go.
I have a completely standard car except for a GTC Stage 2 tune and have over the last 2 Years been very happy with the performance and power delivery. It has done an 11.05 1/4 mile however my main sport is Sprinting, the tune knocked seconds of a typical lap. I am always amazed how "slow" the car feels when I uninstall the AP when taking it in for a service..
Howerver in the tuning world things do not stand still and both the Cobb & the ECUTec have developed in leaps and bounds over the last 2 Years. Remember as well as Thistle who is responsible for some of the mapping inovations there is a large team back at Cobb in the US.
The Cobb AP is however far more than just an ECU tuning tool. ( I could say it's a way of life, but that might be overstating it a bit.
) I also have and use the TCM upgrades that the Cobb allows to the Launch and look foreward to LC4 that I am sure will emerge one day. I have frequently used the DTC reset functionality and value the clutch relearn and adjust that the Cobb makes possible. Looks like we will also soon have the ability to relearn TPMS codes for alternate wheels. :thumbsup:
So all very positive for the Cobb, but I will admit that if I was making a decision Today it would be more difficult. Now that my car is in it's 3rd Year I will almost certainly start taking it to Litchfield's for servicing.
Because of that I will look to them for oil, brake disk & pad change advice and if I can be persuaded that changes to the exhaust or intakes can be done and still stick within the noise limits for places like Goodwood & Castle Combe, then it's all to easy to have them do that as well.
So at that point it would be very convenient to also have the ECUTek tune and have it all neatly looked after by the same people??
My gut feeling of an answer is that the performance gains of both tuners are similar. I would however like to see a few graphs for the ECUTek, there are loads around for the Cobb, but I have yet to see one for the ECUTek? At any point in time one may have an edge in a particular area, however they are keeping eachother honest, inovating of their own right and also responding to what the other does. Having them both is of great benefit to us all. :thumbsup:
I do not know if the ECUTek can do on the road logging? But would be very reluctant to give up this feature. Having Ben / Thistle able to look at and respond to real world logs, on the road, track and drag strip is very valauble and gives great peace of mind.
However if you live close to Litchfield / use them for servicing I would say it makes sense to go with ECUTek, if not then you are probably better off with GTC / Cobb.
All of that said even if you go with ECUTek, I would still advise owning a Cobb just for the TCM functions, DTC reset, TPMS learning etc.
Rich