The club level rooms offer some additional services not found in others. For starters, there is usually a club level lounge. Typically, they will serve a continental breakfast, as well as snacks (hot and cold) in the evening. Usually you must purchase alcoholic drinks. Also the club level rooms have a few extra items (depending on property) like bath robes, bottles of water, or one of those copier/scanner/printer/fax machines. The club level is usually on the higher floors of the hotel. I too have found I am usually upgraded to the club level, but was once told this is only for platinum. You can also occasionally get a suite upgrade if you ask, or a junior suite.
Platinum members also receive a welcome gift on arrival, and once (as a gold) I got something like this at the ATL airport Sheraton. It was like a cheese/fruit plate waiting in the room. You also get a 50% bonus on the Starpoints earned.
I am also Hilton Gold. Unlike Starwood, Hilton specifically indicates a Gold will get the club level. If there are no club level rooms available, or if the property does not have a club level, the Hilton Honors program states the Gold VIP is to be given free continental breakfast. Starwood does not have this provision. If you stay at a hotel without a club level, you'll have to buy your own breakfast. Hilton also gives you miles and points.
On the Starwood plus side, they have the Free Fridays, and no blackout dates or capacity controls. Just for fun, I called Hilton to try to book some random nights at a near-by Hilton in BOS. Because awards are cpacity controlled, I could not get the nights I asked for (just nights near my date). Also Hilton does not have a Free Weekend type offer.
During last fall, SPG did have some promotions where members could earn some extra bonus points. Let's hope they have another such offer, after Free Fridays ends.
Personally I am thinking maybe of shooting for SPG Platinum, or the other option might be to keep both SPG Gold and Honors Gold for a better selection of hotels. Overall, I have been happy as a Gold...though of course there are those exceptions like in any program.
Good luck, and welcome to SPG!