This is a REALLY tough way to choose components for your panel because it's very, very subjective and barely objective. It's hard to take what each EFIS mfgr tells you either at a show or in their marketing literature and mark it down as a check mark for a certain or given function. Let's say you have function "x", it may be only 20% complete from one mfgr, but 100% complete in another, but on paper both could be listed as having function "x". Just because an EFIS mfgr tells you they have (or are going to have) an autopilot doesn't mean the autopilot works well or functions well in comparison to a stand alone AP....some do and some don't.
Along with that problem is the other subjective things that really can't be put on paper. Some time ago someone tried to "score" and weight various things on a spreadsheet mixed with pricing to give some sort of rating, and to be quite honest it was almost entirely useless as a real tool. The fact is you can't easily just put a spreadsheet together because it's just not that clear. I've seen at least a half dozen such attempts over the past few years - none of them particularly useful in the end.
You also have to factor in what you're going to do with the plane, the mission of both the plane and pilot, experience of the pilots, comfort level with various technology, and couple that with each persons individual desires as it relates to what they feel is important.
Here's what I tell my customers. Figure out what you want to spend first (within at least a rough order of magnitude). Second, decide what you want to do with the plane. Lastly, decide what the best value verses requirements are for a unit.
Probably the most common question I get is "which EFIS should I buy" and the truth is that there is no single solution that fits everyone's requirements. Some are driven by budget, some by requirements, some by functionality, some by what their friends have, some by aesthetics, some by ergonomics, some by manufacturer, etc.. For example, some people might be more concerned about the potential future financial health of a small EFIS company as compared to someone like Garmin. Others like the way a screen looks and ignore anything relating to the company. Some people like the representatives from a company and base their decision as much on the people as they do the product. Others care more about the technical specifications of the sub-components in the products. Over the past several years a lot has changed. Blue Mountain is out of business, OP Technologies has had major issues, and we all know of the Chelton mess. All three companies at some point never appeared to even have a hiccup.
I'm pretty sure I could make a spreadsheet that would skew the decision or choice of a product to any number of manufacturer's benefit, but that wouldn't be a very good nor accurate representation of the real world when it comes to EFISes.
I wish I could easily tell you what is the best way to go, but it's just not that easy.
Anyway, I think a better use of your time might just be a few minutes on the phone with someone who can give you some good objective advice that isn't tied to a particular mfgr.
Just my 2 cents as usual!
Cheers,
Stein
I've started a spreadsheet of possible panel components (EFIS/EMS, radio, nav, transponder, intercom, GPS, etc.) versus features (cost, subscription costs, weight, maturity, etc.). It's kind-of overwhelming for my geeky, get the best for the least personality. 
