I see that you bought the Exedy chromoly flywheel - seems like a good choice, It was one of the options I was considering last fall.
Other than what has already been said, another benefit of chromoly flywheels is that they are usually one piece, machined from a single piece of chromoly. Aluminum flywheels are at least two pieces, consisting of an aluminum center bolted to a steel outer ring. The steel ring is necessary as a starter's gear would quickly wear down an aluminum ring gear.
I bought a Fidanza for my street car years ago and have been happy with it. If I had to do it again, I would go with a single piece chromoly. Actually, I installed Maruha's Power Clutch system in my race car at the end of the 2009 season.
Here's some info about my Maruha Power Clutch System.
http://web.me.com/willm/Site/Engine_Build_%26_Track_Blog/Entries/2009/10/1_Maruha_Power_Clutch_System.html]Will's Engine Build / Maruha Power Clutch & Flywheel
Follow the link at the bottom for more pictures.
Though I haven't updated my website with driving impressions, my overall impressions have been great. I'm very satisfied with the clutch and pressure plate, and the service I received from Maruha. I asked Maruha a bunch of questions before ordering this part and was surprised to hear that many of Maruha's customers use the power clutch system on their street cars. I figured the metal non-sprung clutch would be unstreetable, but according to Saiji at Maruha, many customers are very happy with it. Now that I've driven the car on/off the trailer, on the dyno, around the block, around the paddock, and on the track, I actually believe it. Pedal feel, super-fast shifts, and the willingness of the engine to rev, are all awesome.
Here are some examples of one piece chromoly flywheels vs. 2-piece aluminum flywheels:
Fidanza Aluminum (2 piece, bolted together)
ACT Prolite Steel (2 piece, pressed together)
Maruha 01R Type-C Light (single piece)
Exedy Chromoly (single piece)