Those are no brainer decks... And I would argue it is not best to use 6 shriekers in earth.
You can see the light deck has 6 blessings in it and only 9 creatures. That's why I wouldn't call it a creature rush, but I guess you could. A creauture rush can still go on, if half the units get killed.
Beating AI3 may be simple, but that is not what I'm concerned with. No, use 6 graboids, 6 golems, and throw in a couple of reverse times and basislik bloods.. It is not only fast but you might also stay alive if it gets tough. I've haymakered plenty of those light decks... You just cast a few spells on the blessed pegasuses.
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So that is why I think plain light is defensive. You hang buffs on yourself that may not work, and you heal yourself... It gives the opponent a totally free game. It can't attack an enemy creature in any way, it doesn't target any permas. That is why a lot of rainbow decks borrow cards from entropy, aether, gravity, fire, earth and time.
Here's something:
''The trials listed have been tested for only 50 games but should be fairly accurate for determining deck speed.''
Shrieker Rush: 7.688 turns to win,
Mono Light Blessed Pegasus Rush: 7.300
You cannot really make much of a claim based on 1/3 turn... Especially not with only 50 games and a crude earth deck to compare. I would never use 6 shriekers, not even elite shriekers.
Anyway I might try that some time, but the AI3 was not really my point. I was more talking about earth VS light. Ah well, enough from me for now..Keep voting guys.