They have never competed events using just same type of cars. In Finnish Championship last year they had two tight events, when Lappi was driving much better car than Nikara (Fiesta S2000 vs. Evo 9) and in Lapua Lappi was able to beat Nikara just 1,8 seconds.
I witnessed the situation when Ari Vihavainen was out off the road and Nikara had to slow down and lost at least 3-5 seconds, so he would have beat Lappi then. But have to remember that there is very fast roads in Lapua area and Mitsubishi were suitable to those roads, but there was also smaller roads when Fiesta will be much faster. I know also that Nikara´s aim in this event was to test Yokohama´s new gravel tyres, but the delivery was late from GB to Finland and he had to use his last season´s Pirellis and had only three new tires for this rally.
Here you can see the difference from the same stage. Nikara was faster this time and was able to beat Lappi by 2,6 seconds.
Lapua 2012 SS4:
Nikara, Evo 9:
Lapua SM Ralli 2012 EK4 J.Nikara - P.Nikara - YouTube
Lappi, Fiesta S2000:
Esapekka Lappi Media
The second time was in Merikarvia and Lappi was leading all the time, but Nikara won one stage before he crashed out off the rally during the last stage. Lappi´s lead was 18,8 seconds. The last stage was a massive 44 km, so it was not yet clear who will win and Nikara was really trying, but it ended when rolling the car. Lappi was driving flat out also and he almost had big accident, but was able to avoid it and won the event.
So we can not say if Lappi or Nikara is faster. I know that many will vote for Lappi, but I am not sure yet. Lappi has to show some more results abroad. It seems that Lappi is more reliable than Nikara, but if Jarkko is able to get same kind on of resources to test the car before the events it is clear that he can stay on the road much better.