Lvl 5 is superior. Apologies for using the old terminology.
You are paying $50K for an exceptional trainer right? Exceptional staff salary increase should be higher than 2%. Not sure how much exactly though since I don't have one. Maybe you can advise.
This is also another good point to consider when assessing whether you can afford a staff or not. For TerFu's case, his exceptional trainer already costing him $50K/week. Although, exceptional trainer salary actually can be as low as $21K, it is still not worthwhile for TerFu to change trainer as it will cost about $1M to bid on another exceptional trainer.
It will only be worthwhile for TerFu to consider bidding for another exceptional trainer if his current trainer salary go as high as $60K. By then, he would be spending extra $39K and if you multiply by 26 weeks (2 seasons), it would cost him extra $1M ($39K * 26). Plus, this hasn't taken into account the salary increment every week. So only when the salary goes as high as $60k/week then only it is worthwhile to consider spending another $1M to replace with a lower salary exceptional trainer
Hope you are not lost by now, but this gives a rough idea on the real total cost of ownership of a higher level staff. Don't just consider current salary, but also need to project how much you will be paying for staff for the next 2-4 seasons.