I just go until I get cited by the mods
Anyway for a 240, you are looking at a combination of canisters or sump(which you can do wet dry or submerged).
Advantage for Sumps:
1) great for DIY
2) Potentially can be made very cheaply
3) Open system
4) maintenance can be easier
5) potentially have larger capacity than canisters
con:
1) Open system - easy for people like my six year old to mess with(or other things to get in)
2) not as quiet
3) Some uses old secondary tank may be prone to leaks
4) unless used with a canister, difficult to have a backup in case of say pump failure
For canisters
1) easy to setup
2) modular design easily backed up or design redundancy in the system
3) closed system not easy to tamper with
cons:
1) for the easiest setup, hard to conceal intake and output ports
2) Can be hard to service
3) Some modules maybe prone to leak due to faulty O rings, lid design etc
4) more expensive for better models...not DIY friendly...