We've stayed in the main building a number of times and we've either had lagoon view, which looks out over the theme pool, beach and Epcot in the distance or marina view which included a dead center view of the Castle. You can't book a specific view in the main building, but you can put in a request for what you like. Pretty much it's lagoon, garden or marina.
As others have mentioned, there are two levels of concierge service offered at the GF. What's considered full service is available in the main building, also known as the Royal Palm Club or RPC. Sugar Loaf houses the light concierge option or lodge concierge as it's sometimes referred. Depending on your season of travel, the price difference can be in the $150 to $200 range per night. The only basic difference between the two is the lounge. Up until that point, you will still receive the same pre-planning services from the IPO staff, private check in, on site assistance, same room amenities, package delivery to your room, etc. In the lounge, Sugar Loaf does not have the extensive late night dessert offering that the main building has and neither do they offer wine/beer or cordials complimentary.
Just my opinion, but I thought that Sugar Loaf had a cozy bed & breakfast type feel to it. The on site concierge staff sit in the same area as the lounge, which has the food offerings, drink station, sofas, tables & chairs. This can make for a more personalized, homey atmosphere. All this is located in the ground floor lobby. The lounge doesn't have any TV's. The specific food served, is the same as what you'd receive in the main building (with the few exceptions that I noted above). If you wanted to escape someplace quiet to read your paper and have a cool drink, this is the spot. Room views range from garden to marina, where you could possibly see the fireworks by looking off to your right. There is very little chance that you'd see the castle though. Types of rooms available are standard and lodge tower. There is no additional cost for a specific room or view type, you just request what you'd like through your pre-planner.
The main building is spread out over 3 floors, all of which look down over the main lobby. The concierge staff sits on the 3rd floor, the lounge is on the 4th and there is a small, quiet sitting area on the 5th. I already mentioned the views available for request here. As for the rooms, you can pay for standard or pay additional for deluxe or honeymoon (most of which can be found on the 2nd floor). The lounge is bigger than Sugar Loaf's and offers more seating, 2 TV's and the addition of wine/beer, evening cordials and more extensive desserts. I used cozy, bed & breakfast to describe Sugar Loaf, for the main building, I'd use ambience. Not to the point where I'd ever feel uncomfortable bringing my children or myself, it just had a little something extra. For me, it's the opportunity to sip a glass of wine in the lounge while looking down and hearing the GF Orchestra play on the balcony below.
It's really a matter of personal preference and if you need to fit within a certain budget. If you look at the rates, you can get a Sugar Loaf concierge room for about $50 more per night than a lagoon view. Some wouldn't want to give up their lagoon view for anything, but it's a nice way to experience concierge and don't let the term "light" scare you away. I've enjoyed both levels of service there.
Tammi