Sigh. Another "best filter" inquiry.
There are many great options for your tank. It depends on what you want to spend and what you want for your tank.
I'll throw you a few quick bits of info rather than recommend one thing over another:
For your wallet's sake, go with a HOB. A smaller tank can do very well with one of these effective and very easy to use units. Maintenance is usually a snap as all you need to do is rinse or replace the cartridge whenever needed. They require no complicated assembly and are cheap to purchase.
Good choices in HOB are of course Aquaclears, Penguins and Whispers.
Aquaclears - offer great flexibility in media, have adjustable flow rates, are readily available and are very good at what they do. Downside can be that they have more bypass than Penguins and Whispers and are known to make a little more mechanical nose.
Penguins - are mechanically quiet, though some people complain about the biowheels being a little splashy. The biowheel is a good means of keeping bacteria going when you replace the cartridges (which can be pricey) and they offer no ease in customization since unlike Aquaclears, you just have that one cartridge rather than layers. They lack adjustable flow rates but on the whole are more effective at mechanical filtration than Aquaclear since they are very secure and tight fitted media-wise.
Whispers - Have been around for a really long time. They offer the cheapest filters and cheapest cartridges (which can be filled with a variety of media) and have a permanent sponge for biofiltration. They are known to be quiet - but are also known as the least reliable when it comes to construction quality.
Recently, Rena has introduced something called a Smartfilter. This is a HOB that functions somewhat like a canister in allowing massive amounts of media and several chambers. They are very pricey and reviews are generally favorable but mixed. I am planning on taking a chance with one eventually just out of curiosity.
So I hope this just confuses you more. Truthfully all you will get from people when you ask these questions would be their personal favorites which means very little.
Canisters: well, if you want to spend the money and invest the time in these, you will find they are the best way to filter a fish tank. They do of course require lots of effort in assembling and maintenancing. But they yield the best results and also give you far more flexibility in choices of media and media configurations. Not to mention that they are the most cost effective to run over time as you can go months, even years without ever having to purchase new media. I have sponges in my Fluval 104 that have been squeezed clean every month for almost three years and still show no signs of needing replacement. Try making a Penguin cartridge last more than a few months at best before it is just a nitrate factory.
Most people claim that Eheims are some kind of god of canister filtration. Truth is that Rena and Fluval do just as well a job of keeping your tank clean. Eheims are expensive but offer a very reliable product. There are some Eheim classics that have been running for decades without a single repair. Very easy to operate and offering many good features. Some say they are worth the money, others say it's a waste. Personally I'm of the opinion that they are overpriced.
Fluval - These Hagen products have a controversial reputation. Some people end up with units that are nothing but trouble. Others find their kinky hoses quite annoying. Still others think they are amazing. I have a 104 and I love it (except for the kinky hoses.) It's silent as dead air and never has given me a mechanical issue. But still, I am wary of buying another just based on the commonality of others' bad experiences.
Rena - highest flow rate to cost ratio of all quality canisters. Lots of media baskets. Easy to use. Very effective at keeping the tank clean. But have these ugly blue intake tubes.
Marineland C Series - getting rave reviews from all who use them. Might just be the next great canister filter set to topple Eheim. Somewhat pricey however.
Penn Plax Cascade - AVOID. Garbage.
Hope this helps!!
(I would buy an Aquaclear or Penguin.)