I've been at Mercury for a few years now and love berthing there. Very friendly marina with great views, although it will cost more than Cobbs. Depending on the berth location it can be tricky mooring/departing on strong ebb tides so choose location wisely. The closer to the bank side the better.
You can also fuel up at the MDL Port Hamble pontoon.
There's an on site restaurant and bar which serves good food and drink but can be a little pricey. They also do cooked breakfasts but I tend to go into Hamble village for breakfast. In my opinion the sausages are poor quality at the marina.
Plenty of pubs and places to eat in the village which is a half hour walk. Plus a Force4 for all your boaty bits.
When we were at Cobbs we had the option to berth at Mercury with freedom berthing. I really liked the rural feel and general friendliness of the marina and the variation of cruising destinations.