I have been wondering the same thing for a year HaHa! Fluvals seem to be a popular choice, but for me, after reading countless reviews I finally ordered my canisters; Rena Filstar XP. I went with these because I read a lot of folks new to filters had trouble with leaking Fluvals (from not aligning everything correctly from the start) and me being new, thought it'd be best to go with Rena Filstar which didn't give people this problem.
got a rena xp1, had it for over 5 years, havent had an issue with it. I also have an eheim 2213 and that's also an amazing filter. I like how the rena is so easy to prime, if something goes wrong i can easily re prime it(no need to suck on anything), compare to the eheim. Though the eheim does have more media space.
also, when it comes to aesthetic, the eheim has a better designed body imo. It's sleaker and the pipes are thinner compare to the bulky size of the rena. The eheim's green and blends into the aquarium a little better compare to the blue/black of the rena