I have to big preferences that i choose for two diferente reasons. Sampaoli and Koeman.
Sampaoli because tatically he is brilliant, he did a very good job with Chile(their defense was so unortodox and at the same time so good) and he is doing a great job with Chile now. He doesn't have Barça dna but at the same time the players love him and he has a similar philosophy. Also he unlike Martino, he is proving himself in Europe. His Sevilla is doing a great job in La liga and also at Champions league.
Koeman is completely different. He is not tatical genius like Sampaoli but he is competent, and with his background and experience that may be enough to put us playing great football and winning titles. Looking to his carrer he starts in Vitesse doing 4º, nothing special because Vitesse was doing that kind of results. Next season he goes to Ajax the half of the first part of the season. He got the team in 2º and they didnt won the league in 3 or 4 years and he won it along with the cup. Next season he got 2º if i'm not wrong and the other he won the league again and the other he did a bad season. The next season he went to Benfica, they were the current league champions despite the awful football they practise with Trapattoni, Koeman did bad here, he won the supercup and did 3º the league but on the other hand he put Benfica in the QF something that only happened 3 times in my lifetime(i'm portuguese). After Benfica he went to PSV, he inherited the team of Guus Hiddink and was narrowly champion despite a serious of injuries that affected his team. Next season he went to Valencia, he had a nice team but didnt built it. He got the team in November and did even worse than the previous manager leaving the team 2 point from relegation in 15º. But on the other hand he won the Copa del Rey eliminating in the process Barcelona and Atlético. Then he went to AZ, where he inherited the team that was league champion with Louis Van Gaal and did badly. Next season he was hired by Feyenoord a team that before him did a humiliating 10th place and before that season a 4th place. In his first season in Feyenoord he managed to do second, something very interesting because of the conditions. Next season he did a 3rd place and the other another 2nd. So he put Feyenoord competitive again. Next season he went to Southampton, he had the task of suceeding Pochettino who did a 8th place in the premier league. Also, the most influential players were sold if i remembre well, Lallana, Lambert, Shaw Lovren. No one believed Koeman would do a good job but he rebuild the team and managed to do 7th place and the next he did even better better, a 6th place, highest premier league place for them with the record number of points for the team. This season he signed to Everton and he is doing an interesting job. He is the leader of the rest of the normal clubs in premier league. He is doing a 7th place in Premier. His predecessor did two consecutive 11th places.
So Koeman is an interesting coach and he has a unbelieveble experience. He won the champions with PSV and Barcelona(the first we won, with his goal in the final if i'm right) he won a number of eredvisie and la liga. He was a key elemento of the dream team of Barcelona and also the Netherlands team of 88'. The man, has not only Barcelona DNA in his veins, but also a champion dna. He was trained by champions, he was colleague of champions and he himself was a champion. Also, he was assiatant coach of Guus Hiddink and Van Gaal at Barcelona. He also managed interesting players like Villa, Ibrahimovic and Lukaku.