Copied from another forum, but very useful...
Here's my unofficial guide to cams for people who are mechanically challenged like myself. I recently spent weeks researching cams before deciding on the hot rods and I'll pass on to you what I learned in a nutshell.
NSR Cams
Most popular - FRPP Hot Rod Cams, Detroit Rockers by Comp (sold by Brenspeed)
Positives - Good all-around cam. Good driveability. Minimal loss of low end. Nice lope. Some power (around 25rwhp with LT's and cmdp's), most affordable since the only thing that needs to be replaced is the cams and 2 cam bolts.
Negatives - You can get a little more power (12-15 rwhp) from an SPR cam. IMO the Mutha Thumpr's do sound a little bit better although the hot rods sound pretty damn good.
Something to consider: If you get your tunes from bama I would go hot rods over detroit rocker. I contacted several users on here who run a bama tune with hot rods and they all said it was spot on and mine is as well. I could not find a single instance of someone using a bama tune on detroit rockers. This is because they are sold by Brenspeed and most use a brenspeed tune with them.
Less popular - Comp 127200 and BBR Stage 1
Mutha Thumpers (Comp 127020)
Technically an NSR cam although you will need to install lockouts to lock out the VCT.
Positives - Best sounding cam in my opinion. They pull hard as hell up top and give a little more power than the NSR cams.
Negatives - I drove a car with Mutha Thumpr's and 4.10's and it loses so much low end they felt like my buddies 3.31 gears. The driveability is pretty bad on them. Really annoying just trying to get out of the parking lot without bucking or stalling and I consider myself pretty good at driving stick. And it's not just parking lot speeds, it bucks some even at higher speeds. Also, you'll have to spend a little more money on lockouts.
Something to consider - If you really don't believe me and think you won't mind the loss of driveability, read this thread. Mutha Thumprs installed/Not so happy - Ford Mustang Forums
SPR Cams
Most popular - Comp 127500, BBR stage II
Positives - With proper tune can maintain driveability and low end similar to NSR cams. Give more power (12-15 rwhp) than NSR cams.
Negatives - Lope the least and you will have to spend more on parts because you will need both VCT lockouts and new valve springs. This makes the install more expensive or difficult as well (depending if your doing it yourself or not).
There are other cams out there but these are the most popular ones.
Just FYI, after I added full exhaust and hot rod cams I had my car re-dynoed and I picked up 43 rwhp and 21 ft-lb tq. There's no way that was all from just long tubes. I figure around 15 was from the LT's and around 25-28 from the cams. These numbers aren't perfect because the first dyno was dynojet STD and the second one was dynojet SAE corrected at 0.97. I also swapped from 3.55's to 4.10's in between dyno's. It still gives you an idea though.
Also, if I gave out any misinformation here, someone please correct me.
I can't imagine the difference being significant though. And they look 100 times better painted. Sorry mustangmike, didn't intend to highjack your cam post. 
