With the number of nights, you'll nearly make Hilton Diamond which is sh*t hot compared to IHG Platinum, plus you have more choice with Hilton in Cairo than IHG
Downside with hilton is redemption is higher than IHG, but the hotels are generally better in UK/europe plus benefits of gold/diamond are way better.
If the price is right, I'd do Hilton. The massive points bonuses are gone at IHG and they don't compare well anymore, even with free wifi(crap speeds) and vouchers for plats. Unfortunately, IHG is more convenient for me at the moment and I had to give up diamond...very sad day!!
Fire off an email to CS, see if you can get a challenge to fast track, 50 nights is attractive to any hotel chain. I got diamond for 20 nights that way