JW Marriott Aerocity is the best hotel of the bunch for Elite recognition. But 6 nights - might be difficult to pull an upgrade because hotel is extremely busy in these days. From that perspective Le Meridien might be better.

JW Marriott lounge is excellent, one of the best breakfasts in India too. The rooms are great, hopefully one can pull at least a 1 category upgrade for Platinum.

Sheraton has bad older reviews on Marriott website but recently renovated (and good reviews on TA/Google). I will probably be staying there in March for 1 night. I would stay at JW but it is like 40k INR/450+ USD per night then.