Williams IJ has so much more to offer than IJ4 in terms of rules, shots, aesthetics and sound. IJ4 looks like Stern did it a bit on the cheap side. It also came out when Stern was in a semi chaotic phase with the company and it shows. Did they ever complete the code for this one? (not sarcastically asked).
I've played both but never owned either. I should for being such a fan of the movies. If I was to pick one up I'd go for WMS IJ.