The October 2005 issue of R&T has reviews of both cars:
Compared with the sports car's new rival, Pontiac's Solstice, the Miata is 0.4 sec. quicker to 60 and beats it in the slalom, while the American is slightly better around the skidpad. Drive them back-to-back and you'd likely find the Mazda a bit crisper in handling, the Pontiac somewhat smoother in ride, but the duo walking both sides of the ride/handling compromise with ease.
2006 Pontiac Solstice
0-60: 7.4 sec.
1/4 Mile: 15.8 sec.
Top Speed: est. 120
Skidpad: 0.88g
Slalom: 67.0 mph
0-80: 13.2 sec.
Braking from 60: 114 ft.
R&T Fuel Economy: 21.0 mpg
Balance: Moderate understeer
Base-price: $19,420. (Price as Tested: $23,095)
2006 Mazda Miata
0-60: 7.0 sec.
1/4 Mile: 15.4 sec.
Top Speed: est. 130
Skidpad: 0.86g
Slalom: 67.7 mph
0-80: 12.4 sec.
Braking from 60: 112 ft.
R&T Fuel Ecomomy: 23.0 mpg
Balance: moderate understeer
Base-price: $20,435. (Price as Tested: $27,610)