Thank you all for your advices.
Yea TUI contracts are CDD, proper French temporary contract, it is not a self employed status at all.
Travel service request arround 1000h I believe and TUI does request only a type rating.
Some guys did leave RYR for TUI based in France, but still, if something wrong happens in the industry, RYR will never go bankrupt, whereas TUI will first stop contractors in France for sure.
Although RYR is starting to expand in France, BOD and MRS (2A/C each from april). Still really hard to get.
Hard decision to do I guess.