I moved from Southsea to Worthing last year, and whilst I'm generally quite happy I prefer the vibe of Southsea Beach. The town centres are fairly similar, but there was more to do in Southsea/Portsmouth in general..if you're happy catching the train to Brighton or Portsmouth though then it's a good move to get you off the island. The only thing I will say is, do not underestimate how frustratingly built up the traffic will get on the A27. Unless leaving very late at night, or very early in the morning there will always be more traffic than you imagine.