I sailed with a friend of min who is in my opinion one the the best wave riders in Sweden yesterday. He was using his quad (from another brand) as a twin. For some sailors a twin fin is just hard to beat. I don't know Philips sailing so well, but I suppose it's as simple as that he likes twin fins better and that the EVO shape works better for him than the Quad shape. The EVO IQ is in fact a really drivey shape though. SO as far as twin fins go, you can definitely still put some rail in and get some acceleration out.
If you comparing the EVO IQ 71 and 2010 Quad 71 (which is in fact the old EVO 70 shape) my initial feel after only sailing the IQ 71 one time is that the EVO IQ 71 feels a little bit bigger. The new IQ 71 is super stable and easy though. And I think it will still be awesome in lots of wind and work really well in onshore too. But I got to get more time on it to give a serious comparison.