DETROIT – The Pontiac Solstice won the roadster duel in the U.S. for 2006, but Mazda North American Operations’ top executive is unfazed by the MX-5 Miata’s second place finish.

The Solstice ended the year with 19,710 sales in the U.S.; the MX-5 delivered 16,897, up 72.4%, according to Ward’s data.

MNAO President and CEO Jim O’Sullivan says he puts little stock in the results.

For starters, the customer base for the two vehicles is totally different, O’Sullivan says in an interview here.

Additionally, “we could have sold a bunch more MX-5 Miatas if we wanted to,” he says, but capacity was an issue. And MNAO had no interest in offering incentives for volume sales of the iconic roadster.

O’Sullivan also points out the seasonality of convertible sales, and the fact the retractable hardtop version of the MX-5 did not bow until October, with many areas not receiving the model until November.

He says he is looking forward to a full year of hardtop sales, expected to prove popular, as the new top does not add weight or sacrifice packaging but provides a new level of “seasonality” and addresses security concerns consumers have with soft tops.

“And one year does not necessarily define success or failure,” for the global MX-5 vs. the regional Solstice, O’Sullivan says, especially when the MX-5 “remains the No.1 selling roadster in the world.”

The car has attracted passionate loyal customers, he says, and is credited with creating a segment group that has exploded.

More important to O’Sullivan is the fact Mazda’s total U.S. sales were up 4.0% last year, and the auto maker spent substantially less on incentives.