It's always hard to tell someone what filter to get because as someone else mentioned it is highly based on what is most important to you (flow rate or media basket size or ease of cleaning etc etc). With that said the canisters I currently have running- Three Fx5's and two Ehiem's (the older version of the Pro4's) and I did have a Sun Sun but got rid of it. There wasn't anything "wrong" with the Sun Sun, had good flow and good size baskets, but I just had trouble getting mine to seal properly. I have friends that have Sun Sun's and theirs are fine so I could have just got a bad one. With that said my favorite filters are FX5's. I like my Eheims but the FX5 for me just has everything I like in a canister. Good amount of media, real good high flow rate, primes very easy and I like how it self purges every 24hrs. Usually you can find the Fx5 used in good condition at swaps, local club members, or ebay/amazon for $125-$150 range so that would be my suggestion.
With that said though, that's just my personal favorite filter. Really you can't go 'wrong" with any of the ones mentioned as long as you make sure the size you get is appropriate for your tank size/bio load.
With that said though, that's just my personal favorite filter. Really you can't go 'wrong" with any of the ones mentioned as long as you make sure the size you get is appropriate for your tank size/bio load.