Idk man. As a Turkish dude, my emotions say he should stick with a Turkish lineup even though going international could be wiser choice for him.
Also i believe single nation teams like astralis, mibr (former sk, lg), fnatic at their peek etc. play/played much better cs than any international team could ever play. I guess that is because the synergy is higher with those cuz no cultural/language barrier etc. That is why i always prefer single nation teams over international.