Seems like apples and oranges to me.....
Sunrise is at DAK on the Kilimanjaro safari vehicles with MANY of your closest friends and neighbors (we had 2 full ride vehicles on our safari - so that is about 30 people??) - lots of little kids- lots of info on the various animals - Giraffes, hippos, Lion, rhinos, hoofed animals.....Then we had a super yummy breakfast at Tusker house - best breakfast in WDW IMHO.....The sunrise safari is 10 times better than the regular Kilimanjaro safari because your guide stops the vehicle whenever he spies something interesting and stays put as long as needed to get a great look, plus he answers any questions you may have... - we had a Giraffe about 2 feet from our vehicle - Plus, the animals have just come out, so they are most active (we saw the lion roar - which apparently he only does first thing in the am, like a rooster) - and being the first ride vehicles of the day thru the area, many of the animals are just standing in the road, or very close to it ---
Sunset is an intimate ride around AKL (8 people total) in their specially designed ride vehicle (a van where the roof pops up and you can look out) - followed by a super yummy chef-designed dinner at Jiko - Like was previously posted, you only see the hoofed animals...
IMHO, Sunrise is more about seeing animals, Sunset is more "Romance" - plus there is the cost difference - Sunrise is about $50 each, and sunset is about $150 each.