Marcelino Botin is convinced there is little to choose between NZL 92 and holder Alinghi's newer SUI 100.

But with only two races sailed and each team winning one apiece, it is still too early to say which is the faster craft, Team New Zealand's designer told Reuters in an interview on Monday.

"Knowing whether you are faster is very difficult", he said. "At this stage for us it's still not absolutely clear what the trade off between the boats is".

"It's pretty even...they're better at some things and we're better at others", he added. "At this stage that's all we know. There's definitely not a big difference between the boats."

Veteran trimmer Don Cowie agreed. He said both boats appeared to suit different breezes and added yesterday's win also vindicated the changes Team New Zealand made to its boat prior to the finals.

"We are confident with the changes we made to the boat and we were after yesterday as well (despite losing)," he said. "The changes we made were very small, they all are at this level. But as I said we are confident we made the right calls."

Before the best-of-nine series began on Saturday, there was widespread speculation around Port America's Cup that SUI 100 was a "rocketship" with a more bulbous bow shape than previous boats that would leave the challenger trailing in its wake.

While Swiss-syndicate Alinghi enjoyed a convincing win in its first defence of the 32nd match in the 156-year-old trophy's history, the Kiwis stormed back on Sunday to square the series.

Botin, a Spaniard who also runs a boat design business in the northern Spanish town of Santander, said that even when boats are trialled against each other in controlled conditions it takes months and years to perfect their performance.

So knowing whether SUI 100 really has an edge over NZL 92, or vice-versa, will only become clear the more they race.

Their next encounter is scheduled for Tuesday, and Botin said New Zealand were not planning any major changes before they took to the waters off Spain's Mediterranean coast.

"Not at this stage for sure, but who knows in the future."

Team New Zealand switched its bulb -- the missile shaped weight at the bottom of the keel -- to a flatter and longer one after winning the Louis Vuitton Cup against Luna Rossa.

While he likes the look of the latest Alinghi boat and has studied it closely over recent months, Botin sees it as a very different craft to his.

"We've looked at it quite carefully over the last months and we think it's definitely a fast boat as has been proven here."

The forecast for tomorrow is a light weather one, with wind speeds of around eight to 10-knots, conditions that are supposed to favour New Zealand. But theories that SUI 100 will perform better in stronger winds while NZL 92 is faster in lighter breezes need to be tested.

"There could be something there, I'm not absolutely sure", he said. "We need to go out and race in 16 knots, maybe 15 is the crossover".