This time, I'd like to start with a graph:
As you can see, we have significantly less creatures and sorceries. In return, we get significantly more Instants, and a few more artifacts, enchantments, and lands. There's also a bit less removal than before, while bounce remains the same and planeswalkers remain, as ever, largely irrelevant to limited analyses. We're left asking what these extra cards are, and the answer is more or less straightforward: the number of "utility" cards has gone up, especially in terms of Combat Tricks. It isn't a huge difference, but I expect it's just enough to be noticeable (if they're playable).
The lower number of creatures either means we'll end up playing fewer or, more likely, our bar for what's good enough will go down a little bit. Before, there were 200 creatures per draft. Assuming 15 creatures per deck, times 8 drafters, that gives you 120 creatures being played, or the top 60% of creatures in terms of quality and/or efficiency. Now, we're down to 182, meaning we're up to 66%. That isn't a huge change by any stretch, but my guess is that it will be enough to notice.
More importantly, the kinds of creatures have changed. Before, we had quite a good number of big things floating around; indeed, part of the reason Green was so bad was that, while it normally had the biggest creatures, in triple BFZ, there were a pretty good number of 7+ drop cards anyone had access to. Now, that's not true at all - these cards have all been stuffed up to higher rarities, and some of them now require colored mana. Effectively, the number of truly giant things has been chopped in half - and with fewer scions and less ramp, those 8, 9, and especially 10 drops are looking less castable, further complicating things.
So what qualifies as big now? 5/5 is the top end of normal - there are enough creatures of this size for everyone to average out having 1-2, and only about the largest 3% of creatures exceed that size. In terms of other 'critical size' questions, it's a bit harder to say. 2 is the most common power by by far, and the most common toughness as well, beating 3 toughness by a smidgeon. There are big drop-offs after 3 power and 4 toughness, but enough creatures larger than these that it certainly won't be unusual to have larger creatures.
57% of creatures have power 2 or less. 81% have power 3 or less. Things are far more spread out on the toughness side, with the first several points each adding 15 to 25% of creatures in the format. Toughness overall is a bit higher than power (roughly 10-15%). Compared to BFZ, the average power of creatures is virtually identical (less than 1% difference), while the average toughness is up by a bit under 3%. Of course, these figures are all based on every creature in both formats, and don't necessarily reflect what you'll see amongst playables. The other significant thing to note is that because we can expect more Combat Tricks, and especially because of the Support mechanic, we can probably expect creatures to be a little bit bigger now than these baseline numbers would suggest.
The amount of removal is slightly down overall. However, as many have noted, the quality of removal is relatively high for recent times. Black and White both get unconditional 4 CMC sorcery-speed removal at Common. These are already being predicted as some of the best commons in the set, with the black one clearly being a little bit better, because it's easier to cast (one colored mana instead of two) and can't be removed later (though there isn't much enchantment removal lying around to start with).
There's still a decent amount of conditional removal, too, of course. Some of the individual cards, I'll want to look at in my next installment, but there is a group of such cards - those that care about toughness - that I think are worth pursuing now. 2 damage (or -N/-2) effects kill 45% of the creatures in the format. 3 damage effects pop that up to 69%, and 4 damage increases it to 87%. Of course, there are the same caveats about creature enhancement and playability as before.
Watch out for more on specific cards as well as overall color balance and impressions soon (hopefully in time for pre-re)!