Rumour has it, if you lapse from Gold to Silver, you keep all your inventory space...
This is true.
You do, however lose the following:
1. If you're still low ranking, you do -not- get anymore slots for anything once your gold goes away. So say, if you're a Commander, you won't get any slots from Captain onward for anything. This includes bank, inventory, Boff, and the respec tokens.
2. The EC cap is re-imposed on you if you haven't bought the cap removal. If you have more EC than the cap, then you'll keep that EC, but you won't get any more EC until you to under the limit.
3. You may or may not lose the third character slot if it is empty, I'm not sure about this one.
If I weren't a lifer, I'd be silver right now as I'm not currently happy paying for the game, so I just use the DL exchange to get what I want. If I were a happy customer, I'd be paying for instant gratification.
As for value for money, you'll get more being silver if you don't have many characters. If you have a lot of alts, then all the CP/DL you'll need will add up and make gold a wiser choice.