I was just in Dubai in May and stayed at the Armani & Four Seasons on Jumeirah Beach but also did a site inspection of the Burj Al Arab. scented points are well stated above, groups can surely effect things and it's a fair question to ask (or have your advisor do the homework for you) if it concerns you but it is not peak season there either. Armani is a much more modern/sophisticated vibe I thought. In peak season the Burj bumps prices a good bit so it will change the vibe in the winter.

Personally I'm a fan of the sophisticated vibe and contemporary feel which they both have but Giorgio's styling of the Armani and their lifestyle managers I personally enjoyed, and being in town I prefered but I also live on the beach and thought Dubai's beach was crap compared to where I live...

If staying at the Armani ensure you get a fountain view room to watch (and listen) to the fountains.