Currently I have an S4 NA. At some point in the future I'm planning on dropping in an S5 TII engine in (not 100% sure yet if the ecu will be added before or after the engine swap). When I started on this journey I had made my mind up on the MS3. However now that I am no longer a student and have more disposable income and less free time, the Haltech Elite 1500 is looking very attractive.
On the one hand I do like the idea of the warranty and tech support line. On the other, I like the idea of having access to the source if I ever need to add some obscure feature I want.
How does ease of tuning compare between the two? Are there other factors I should be thinking about?

 

I thought that the firmware was "locked" in MS3 - source code not available.

That said, it is VERY feature-rich, practically anything you'd want to do is already there.

 

Excellent point. Did not realize MS3 was closed source. Still its much cheaper than the haltech.

 

I'm fairly certain the MS3 source code is easily available.

Source code at the bottom here:
MS3 Development Releases - Megasquirt EFI

Just downloaded 1.4 and took a look. Huh, maybe I'll make a silly change so the serial spits out the car name during init on the MS3-Pro on my Cosmo. Ugh, but have to download Cygwin to compile.

 

The new Elite Haltech units are a definite improvement over previous versions. and will accommodate most anything you'd ordinarily want to do.

But ultimately the MS3 is still the most configurable.