They do miss a couple of key things in that chart, for example the 'Hardware Acceleration', yes it is available in ICS but even though ICS is going to be able to run on many different types of hardware that hardware acceleration isn't going to be available on all devices (particularly older models).
Also the 'Voice Assistant' category, yes Siri is on iOS5 but only works on the iphone 4S so listing it as a OS feature when only 1/5 of the devices iOS5 supports can actually use it is a bit disingenuous.
I'm not sure i would say WP7.5's multitasking is 'True', i would put it as 'Psuedo' since it is based on 'background services'. For example if it were 'true' multitasking then if you played a video in an application and switched to another application the video would continue playing in the background, but it doesn't.
The 'Gaming' section is a bit odd too, when they say a 'wide variety' and the other option is 'less variety', what does that refer too? The genres or the amount of games in that genre? I mean i'd be happy with 'less variety' if what that meant was 2 scrabble apps instead of 20 scrabble apps.
For WP all devices that support WP7.5 get all the features of WP7.5 listed there.
After using iOS5 for about a week. I'm 100% sure Mango is better,for the most part. The new notification menu in iOS5 is top notch. That's the only feature that id give iOS5 over Mango. I can't sat anything about ICS because I've never used it.