I still like chao today, I have a ton of them. I have about 3 memory cards of chao data. My fourth one got deleted which ****** me off. I'll tell you a few of mine.
One of my interesting chao is my very first fan character. Darkstar the echidna (yes a knuckles chao recolour) I downloaded a Shiny Knuckles chao a while ago from Ice Sonic palace site. I ported it to my GBA, and onto SA2B.
I then wanted to have a metallic black knuckles chao. So I typed in the metallic black chao action replay code, and it worked. The thing is, it didn't come out just black. It was shiny black translucent, with Cyan necklace, alien green shoes, with evil eyes, and normal smile. I was amazed, and still had him since. He has Lv 45 all stats.
The current chao I'm raising at the moment is Spike, a light green two-tone neutral power/power, so I can make him good for karate contests.
RgxSuperSonic = XD! you are harsh for using chaos blast on them. Oh well,my friend did that, I couldn't stop laughing. I used to use Tails' hover fly in SA2B, so the chao hit the tails, and go flying.
Anyways, my advantages, and disadvantages with SA2B and SADX chao.
SA2B advantages
You can buy multiple items in the black market unlike SADX, which makes feeding, and raising quicker.
You can use chaos drives as well as animals,and if you do the cheap glitch with the repeated chaos drive/animal give, you can get to a very high level within 1-2 hours.
They have a kindergarten/nursery school which they can a variety of things. Draw, play instruments, sing, etc
The animals give chao much more abilities as well as the basic abilities.
Disadvantages
Some gardens are not big, e.g. the normal garden, that's tiny. Although the hero garden makes up for it.
The animals not only give parts, they take parts off, which is annoying if you want to make a certain type of experiment.
The race/karate modes as Blue Warrior said, the chao are automatically controlled apart from a crappy speed boost/wake up booster.
SADX advantages
The gardens are much bigger, and you can explore more around the 3 areas, station square, mystic ruin, egg carrier.
It's much easier to get neutral chao (most of mine in SA2B come from SADX).
With Knuckles, you can dig up invincibility if you dig a lot around the garden, and it's hilarious just running up to chao, and just see them go flying.
The race has some entertainment in it. Chao being competitive to each other, and making grunts/taunting.
You can unlock 2 metallic chao without GBA, and a black chao egg (what's important about that?)
You don't have to run down the chao lobby alley 26 times to get an item in the black market. the doors are open and you just go in like *clicks fingers* that.
I like the teleports. Making it much easier than to run through every terrain to get to a chao garden.
SADX Disadvantages
Chao karate is not in it. (that would of been awesome)
The black market only allows you to but 1 item at a time which takes chao raising longer.
Sonic,Tails,Amy (Haven't tried this with Knuckles, but I think it's possible) can drown in a chao garden (egg carrier) near the level barrier exactly opposite the other far side in the deepest part.
No chaos drives in the game.
Takes longer to get rings to the game too add to chao garden
You can't sell metallic eggs from GBA games (kinda relates to the takes longer to get rings one, so getting rings with AR is the other option)
A different method of obtaining hero/dark chao since the don't have the hero/dark factors in the characters.
I also have Noodles, who accidentaly got deleted... 
He was an Orange neutral chao, with all bunny parts. I also have My Amy chao, who I only raise with Amy. (Used AR for the Chao, and to play as Amy.)
