I have Mega Squirt 3 www.diyautotune.com It has most (if not all) the functions of the "BigNames" at 1/4 of the cost. Downside is, it's more work to figure it all out. The support is there, you just have to look for it, but it is improving all the time.
All are available plus a few others. It all depends on what you are comfortable working with or what your tuner is comfortable working with. Just keep in mind that with the higher end efi systems you will also be getting a data logger. Spend the extra now and you will be much happier later.
I also have megasquirt 3 fully sequential fuel and COP on every cylinder and like mentioned it does what all the others do for a fraction of the cost you have to wire it yourself. Once you get the all the options configured for your setup it works very well. I actually think the MS software is much better than BS3 software.
I had never really messed with an high powered EFI car... With that being said when it came time to get the electronics and after making phone calls talking to sales reps... we finally went with the FAST XFI 2.0. This is for a turbo'd LS motor FWIW...
There are others also but unless someone is knowledgable with EFI in general they would be better-off using a system that others around them are familiar with. Some of the systems are easier than others for newbies for sure.
I have MS2extra on my truck, but it's slow. I paid 200 bucks for the computer.
I'm surprised to hear that some standalones don't come with datalogging functionality out of the box? WTF.... It's amazing how little some expensive setups can do compared to megasquirt. The tuning and log analysis software for MS is absolutely top notch. Tuner studio and megalogviewer. Both by Phil Tobin www.efianalytics.com
If I wanted to pay big money for a standalone, it would probably be BS3