only striker 4 here bud.
I tried looking at both units and the obvious difference the 5 inch screen would be nicer than the 4 and i believe it comes with a ice ducer 150-240 kHz, 250W which differs from my 77 khz and 200 khz dual beam. Im very happy with the 4 so im sure the 5 with bigger screen will be that much better if your willing to fork out the money.
I have not used my showdown since i got this unit as well. Happy with the garmin unit.