Cassette Adaptor vs FM Modulator

I have an fm modulator and the sound quality's great. I can't tell the difference between it and a CD, but then someone with an extremely expensive system and acute hearing MIGHT hear a slight difference.

If you have the aux input already on your head unit, by all means use it. But if you are trying to decide between buying a new head unit or an fm modulator, I'd say go with the fm modulator (cheaper and sound quality isn't much different).

Now, fm modulator isn't to be confused with an fm transmitter. I have a friend that has tried both the fm transmitter and a cassette adapter and he says the cassette is a little better, but nowhere near as good as AUX or fm modulator.

I saw in another thread a link to one for $30, but the one I bought was $50. But keep in mind that the fm modulator is a lot more work to set up than the cassette adapter (although IMHO it's worth it). The cassette adapter you just plug right into the cassette player and you can begin using it. The fm modulator will require you to do some work "under the hood" and actually hook wires up to stuff. Since i'm not good with cars I had the guys at best buy do it for me which added a little to the price.

From my experience (comparing FM mod to cassette adapter):
? FM modulator provides better quality
? FM modulator costs more
? FM modulator is harder to set up

If quality is a major factor in your decision, then I'd say go with the fm modulator. If you are willing to sacrifice quality for price or you want something that can easily be put in multiple cars then go with the cassette adapter (like if you go on a lot of trips and get rental cars).