The IGA lounge is NEVER EVER a better option. Forgetting whatever work is currently going on, it is often as crowded, if not more than either TK lounge, Entering is ALWAYS a mess, with all sorts of paid people, whether Priority Pass, various Bank credit cards, whatever causing huge queue's at the entrance, and messing up the airline invitation lounge, general guarantee is that 3/4 of the people in the queues are in the wrong places, and everyone has a problem, not the right credit card, trying to get too many people in, not wanting to pay, etc. Worse the staff is inept, and will do things like double or triple charge Priority Pass when you are traveling with a guest AND flying Business Class, and they will even attempt such garbage when they have been warned beforehand by an airlines country/station manger not to do so, as the operate under the guise that they do not believe that anyone entering from their airlines will not be frequenting the lounge again/often. The only smooth entry is for IGA members, as they do all this to try and juice their IGA membership.Despite recently changing their catering provider, the food is generally uninspired and terrible. When they try and do a cooking station, for omelettes for example, they will have generally ONE PERSON making them, and queue's can be 40-50 people deep. I can go further..........the main drinks fridge has essentially been broken for 3 years now, management is aware, but does nothing to fix it. Ice is never ever stocked anywhere near the drinks, and one is directed across to the "island" bar, where you will be given two pieces. Back of house they do not even have proper commercial dish washing equipment, something that was supposed to have been fixed in 2020 and still has not been. When they try and catch up with the TK lounge by installing a Pizza/Pide oven, it is too small, and generally unmanned anyway.

Like any major connecting airline in the World, the TK lounge(s) get really busy if you are in them between major flight banks. If you are not, neither is very full. My suggestion would be to use the Biz one as you are flying Biz, and it is rarely that bad in normal circumstances.