For things where pressure or narrow flow is important, the Maxijet MP 900 is the best bet, for wide-flow and/or low pressure situations, Koralia should perform better
All the best
Rabbut
Edit to add, the MP1200 has a higher flow rate and greater head-height than the MP900, so again, the one you need is situation dependant...
good choice I have a korelia 2 for my planted 64 us gallon and it gives good flow but doesn't blow the plants apart. I had a majijet mp900 and found the flow too narrow and it blew the plants like trees in a hurricane
Even though this isn't one of your choices, I thought I would share that I've been using the same AquaClear power head non-stop for over 18 years with no problems.