"Didn't Infini-D have a better particle system than Carrara?"

Not really. In fact they are virtually identical. The particle system is pretty much the only thing that Carrara took from Infini-D that actually still looks like it did in ID. (The other that remained the same is the lens flare effects)

The main differences in the particle sys are:

Carrara offers more shapes for particles than ID did.

The birth/death colors that were used to color the particles in ID still appear in Carrara but do not actually function. (which is pointless and totally stupid) To color the particles you must use the texture room.

In Infini-D using collision detection you had the option to have your particles collide with other objects in your scene and bounce off of them. Carrara can not do this.

Carrara vs Infini-D overall are nearly two different animals. Carrara is about 10% Infini-D and 90% Ray Dream. Pinklet is way off in saying that the spline modeler is identical. It's not. It's much closer to Ray Dreams that to IDs. In fact having him say that "almost everything from Infini-D got incorporated in to Carrara." would lead me to believe he wasn't very familiar with Infini-D at all. The reality is that almost nothing from ID made it into Carrara.

If you are familiar with Infini-D's interface and method of performing tasks than almost nothing in Carrara will look familiar to you. Nearly everything you learned how to do in Infini-D you will have to re-learn in Carrara. The good news is that Carrara is pretty easy to figure out so it shouldn't take you long to re-learn them.

The texturing method (which can be tricky at first) is superior to IDs. Once you learn it you'll like it alot. Carrara's render is also superior but that pretty much goes without saying.