There is a fair bit of misinformation on this thread about iGCSEs.
Many of the most selective schools use them...and it's not because they're easier...I mean, come on!!!!
Many of them originally chose them because they wanted to avoid the endless round of sitting units/resits/more units/controlled assessments that GCSEs were embroiled in.
Why? Because this system is very intrusive and makes years 10 and 11 a royal PITA. Also, because thgese schools believed that a terminal sitting of all GCSEs together shows ability. And yes, some tutors at many universities including Oxbridge agree with that.
Some super selection state schools (Colyton is one) understood this and acted accordingly.
Universities which make offers relying heavily on GCSE results (Oxford and Bristol spring to mind) have always given weight to terminal exams.
However, things are being evened up in this regard. No more units.
As for the content. Well they're not that far apart. I personally feel the content of the GCSE in English is slightly better, but the content on the iGCSE in Languages hugely better. A GCSE is terrible prep for an A level in MFL.