I learned to play Pente about 20 years ago or so, (on the 19x19 board, of course). It was a novelty among my friends and me for quite some time, but it wore off when we discovered that the first player usually wins, barring serious error.

So, I gave away my board and set and forgot all about Pente until I started playing Keryo at IYT, as it seemed to be an improvement. (However, I wondered why they used a smaller board.)

I find the keryo13 version fascinating, and while the first player has some advantage, I do not believe it is insurmountable or anywhere near as great as in all the other Pente versions. I do not know what my won-lost stats are as to colors; I've lost from both sides, but only two players at IYT have won more Keryo titles than I have, so these stipulations should carry some weight. (In contrast, I also played some pente13, and it is enjoyable, but I believe the first player has a much more marked advantage.)

Another appealing aspect of keryo13 is the possibility of edge play, which I find makes many games quite interesting because it can cause fortunes to reverse quickly!

I have also tried Keryo(19) here, and it is an even better version, although I don't believe this would in any way undermine the charm of Keryo13.