Personally I would keep looking until I had a flight with a 1.5-2 hour connection...

But if you want to see something during those 22-23 hours go to Madrid, the airport is less remote with better ground transport/cheaper taxis.

While I enjoyed my last visit to HEL, I wouldn't recommend a quick visit in April.

Soon (June/July?) AB/HG will be in oneworld and connections will get easier (at least from VIE).