The topic of ECUs always leads to interesting and heated debates, and everyone has their opinions about it. Unfortunately there is a huge amount of misinformation out there, plus rumours and stories which get blown out of proportion and quickly spread among friends and the internet.
I was an engineer in the aftermarket ECU industry in my previous job, doing everything from software to electronics to technical support, so I've had plenty of exposure to ECUs from various points-of-view.
Although I have only dealt with one workshop/tuner (MRC at Castle Hill) for my own car, I still have a good idea of how most tuners think and the kind of things they overlook, because I've provided tech support to MANY well-known tuners, both good and bad ones, each with varying experience in different ECU brands.
Ultimately the ECU is in charge of everything that happens in the engine, so even if you have all the best mechanical parts, they will be let down if you have a poor tune and/or a poor ECU. However, as track_mr2 said, the most critical functions of an ECU are mostly the same (and very stable) for all ECU brands...provided that the ECU is set up correctly by the tuner! The quality of technical support is actually one of the most important factors when choosing an ECU brand, because that can make the difference between 2 almost-identical ECUs from 2 different brands.
In my opinion and experience, the majority of reported 'ECU problems' are actually tuner problems. Sometimes they have a lacking understanding of one or more important ECU settings, sometimes they run out of patience/interest/time, sometimes they forget about something trivial but crucial, sometimes they make costly and time-wasting diagnostic errors, sometimes the manufacturer fails to provide them with sufficient support, and sometimes the owner of the car makes it much worse by pressuring the tuner and/or providing innaccurate and conflicting feedback about problems with their engine.
Often a tuner (or vehicle owner mucking around with their ECU settings) will ignore or change a crucial ECU setting, and not realise the importance because they don't understand that particular setting. Sometimes that same lack of understanding will also prevent them from ever mentioning or questioning that particular (crucial) setting when trying to get help in diagnosing a problem, so they can end up barking up the wrong tree.
Occasionally an ECU will have a real firmware bug or electronic issue, and this can happen with ANY brand, but this situation is far rarer than people seem to think. Also, an actual ECU problem can often be solved quite easily if the tuner bothers to seek support, and actually follows through on the advice offered to them by the manufacturer.
If a tuner has enough skill, time and patience, combined with a good attitude, then they should be able to get a great result out of almost any ECU (assuming that the ECU has the required feature list). If the tuner is using an ECU that they are familiar with, then of course it will be easier for them to meet those requirements. Having said that, if a tuner insists on using a particular ECU but they can't properly justify it, and/or they clearly don't have a strong enough all-round knowledge of ECUs, then be wary.
Just one more thing. I like to keep a detailed list of every little thing that needs to be done or checked on my car, and that even includes individual settings in my ECU! In my case the ECU is the one thing that I understand more than anything on my car, so I will admit that I'm more likely to do that compared to other people lol.
Even the best tuners can forget a small but important detail or step, but if you keep your own comprehensive checklist then you can be confident that everything will be accounted for in the end.
One of the reasons that my car's build/showroom thread has grown to be so enormous (apart from my regular and sometimes amusing indecisiveness), is because I also use it as an additional medium for 'recording' my thoughts and the progress on my car. It sort of acts as a history of my past checklists, so in the near future I only need to worry about a small to-do list.
I hope that helps!
