Default [Q] Updating Android o/s for Defy

Hello.

I have the Motorola Defy. About a year after I got it I updated to Cyanogen Mod I think version 7.1 which is Gingerbread.

I have issues using VPN on this and always needing to type password is a pain.

Is it worth me updating Defy to something like Jellybean or KitKat and if so is there a Cyanogen mod I can use for this or do you recommend any XDA Developers rom on this site?

Would these versions jellybean and kitkat of Android be okay to run without too many issues on a Defy which is quite an old phone now being 3 years old maybe 4?

I believe there is a tiny bit of overclocking possible with the Defy because they originally limited the cpu to I think it was 600 or 800mhz. 1.1Ghz is probably possible "just". Single core though and memory quite small nowadays.

Is it worth updating Android version on this phone to get another year or so use out of it & revive for a bit longer or would you just not bother and instead get something better?

Do you know if there are many know issues for going to Jellybean or Kitkat or would it generally be better than staying on outdated Gingerbread?

Thanks for your advice

John