Originally Posted by Delectatio

I have stayed in both (and will stay again in both hotels in May).
Eiher hotel is a good choice and both of them have pro's and con's.
The lounge itself is much more impressive at the Bomonti (360° views from the 34th floor, knowing that the hotel is also located on a hill, you will feel like you are on top of the world!).
The Conrad lounge indeed has a terrace but no real views to speak of (It is on the 2nd floor facing the street). Offerings at both are similar.
Outdoor pool is again much nicer at the Conrad (it is well protected from the wind and with nice gardens around, they also make up your sunbed etc.) while the Bomonti outdoor pool is located in an extremely windy spot and despite being large and modern, a bit charmless. But...the indoor pool and spa is again much more impressive at the Bomonti!
If you like 'Western' breakfasts, the Conrad also offers pork bacon and sausages (on request) while the Bomonti doesn't serve any pork. Only a small thing of course but it might be important to some...
Some people complain about the location of the Bomonti but we never had any issues, it is only a 10-12 min walk to Osmanbey metro station (where many high class shops are located, it is also only 1 stop from Taksim which is considered the heart of Istanbul).