It sounds like you've kind of already made up your mind, but you're looking for reassurance.
You really wasn't happy with the colour last time from memory. If you don't feel confident that the current hairdresser can achieve what you're asking for now is the time to change.
Sometimes I would completely disagree and say give them another chance - we're only human we all get things a little wrong some times. But if you don't feel like you have that trust in someone then it's always better to move on in the hope that you will find someone you can trust.
This is a very difficult decision for anyone else to make.
I would agree and disagree that someone who's been in the industry longer might be better suited to the task. Simply because there are plenty of hairdressers with 20+ years experience who still chose the wrong colour or cut someone's hair too short, or over processed their highlights. There are also hairdressers who have only 4 years experience under their belt, but have spent a lot of time on money on education in those 4years and could very well be top of their game.
My best advice would be to book a consultation with whoever you feel more confident. If you're unsure book a consultation with both and then make your decision after that.
There's no right or wrong way to do this because ultimately its your hair and its your choice.
Whichever hairdresser you chose, I hope you get the colour you ask for 
