whats the difference? and which one would you recommend i went for?

thanks

 

Electronic as It gives you far more control

HKS EVC 5 and yep i have one for sale £300.00.
http://www.dpmotorsport.com/parts/hks/home.htm

can be seen working

 

Sorry read it wrong but it dose have a boost gauge on the screen

 

Electronic boost gauges start under the bonnet mechanical.

Whats the difference? appart from the black controller box that never get used for owt!

My Defi unit got used like twice..............

 

The difference is about £250 in your pocket.
For most applications a Motul or Racetech guage, costing around £30 is adequate.
Choice of white or black screen.
Get a scale suitable for your application. No point in having a 3 bar scale for a 1.5 bar car.