This is funny because I just did a bunch of research on this a week ago for one of my brother's friends. My conclusion is that the Mazdaspeed is a better car, as seemed to be Sport Compact Car's conclusion. Here is what I came up with enjoy and make your own conclusions.
<b>Don't buy either one until you have test driven both of them</b>, plus a few others to make sure that is what you want. The Mazdapseed has far more features and was built way better. Companies that helped put it together include; Mazdaspeed, Racing Beat (CA), Sparco, Kenwood, Callaway Cars, and Racing Hart. I haven't seen such research and development for the Dodge, plus everyone I have know that has owned a neon has said that they are the biggest pieces of junk ever and they hate them. It's American, lets face it, America has never made a good/reliable compact car. But if you go by numbers the SRT-4 "looks" good on paper. You would have to drive the Mazda and the Dodge to see the differences. You should be your own judge, don't decide off of pure numbers only.
<b>Quote from Sport Compact Car:</b>
"The Mazdaspeed Proteg gives up 73 hp and a 100 lb-ft of torque to the overendowed SRT-4, and yet it was surprisingly close to nudging the Dodge out of the top spot. The fact is, none of this car's test numbers, not even its winning handling numbers, do justice to the Proteg's true capabilities. This is an amazingly well-sorted car with surprisingly few compromises." <b>He also says</b> "Hustling the Mazdaspeed Proteg down a twisty road elicits the same slack-jawed amazement once reserved for the Integra Type R." - <b>Dave Coleman</b>
There is a link to the articles at the bottom of the page.
<b>Quote from Sport Compact Car:</b>
"Gathering performance data, it quickly became clear the SRT-4 was dominating the straight-line tests, and the Mazdaspeed Proteg was being equally relentless with the handling tests. To break the tie, we took to the mountains and let real-world speed decide the winner. As you have surely guessed, the SRT-4 was the faster of the two, but not by much. It took more than three miles for the SRT-4 to pull an appreciable gap on the Proteg. While not as solid and composed as the Proteg, the Neon still showed decent balance, good grip, strong, fade-free brakes, and of course, staggering pull between the corners." - <b>Dave Coleman</b>
Mazdaspeed
0-60: 6.9s
1/4 mile: 15.4s (I've seen as low as 14.7s)
Skidpad: 0.89g
Slalom: 70.3 mph
HP: 170
Torque: 155 lb/ft
Boost: 6.9psi (easily pushed to 7 or 8psi for 200+ hp)
Compression: 9.1:1
Differential: Limited-Slip
$20,500.00
Neon SRT-4
0-60: 5.6s
1/4 mile: 14.2s
Skidpad: 0.85g
Slalom: 69.0 mph
HP: 215
Torque: 245 lb/ft
Boost: 11-14 psi
Compression: 8.1:1
Differential: Open
$19,995.00
Yahoo Autos straight comparision
Car and Driver forum about SRT-4
Car and Driver Road Test Mazdaspeed Protege
Sport Compact Car Mazdaspeed Protege
Car and Driver Road Test Dodge Neon SRT-4
Sport Compact Car Dodge Neon SRT-4
Tough Crowd Comparison Test (Sport Compact Car)