Let me start by saying that I'm a total newbie so you know how seriously to take my advice
I have a Fluval 304 cannister and an Aqua Clear 300 on my 55 gallon (200 litre) tank.
I bought the Fluval rather than the Eheim Pro because it was half the price... I was a bit wary because a few people on here were saying that they can be difficult to service and I am (how can I put this nicely) "technically challenged".
Well I rate the Fluval as idiot proof - I've had no problems setting it up, starting it, restarting it after water changes (it does that itself) or cleaning it.
If you did buy a cannister and serviced it before you went away, your wife probably wouldn't have to touch it other than turning it on and off for water changes. So service intervals is something else to consider in your decision.
The Aqua Clear has to be manually refilled after water changes but again that's a no brainer...