Which is smartest?

I suspect this depends somewhat on how similar the games are. If they're simply about the same subject, then it may not matter much either way. If there are overt gameplay similarities as well, then being first to market may be prudent.

The conventional wisdom is that no one is going to steal your ideas. This generally applied to pre-published designs, but I think it must apply even moreso to games that are on the market, or at least, if your game is already on the market, your sales shouldn't be hurt by someone borrowing from you. One example is the game Citadels, which directly lifted a mechanic from the game Verrater, and by broadcasting this loudly, probably resulted in a lot of sales for Verrater as well. And if your game makes a big enough splash for the big company to even notice it and want to borrow from it, that probably means your game is selling well.

The one cautionary note is that you shouldn't rush your game to publication just for sales reasons unless it's really and truly done. If you don't playtest thoroughly enough and end up with some flaws in the game, your game will instantly be declared broken and sales will grind to a halt. So, by all means try to get your game out if you can but don't do it at the expense of thorough playtesting.

Good luck,

Jeff

Ideally, you should be playtesting your game with a broad and varied enough audience that you get that kind of feedback before the game is shipped to stores. It's probably impossible to iron out every wrinkle in advance, but you should certainly try, and at least convince yourself that you've gotten as much feedback as was realistic.

Again, I really don't think this kind of thing happens. You can't not market your game for fear that your ideas will be stolen!

-Jeff

Things REALLY depend on how unique your idea is.

I really wouldn't put it out until it is truly done regardless. I watch games of a similar theme like a hawk. I play them. I make sure that my game is still different. I know that I do not have the money to market it myself, so I am at the mercy of game companies.

The KEY to playtesting is this:

People you don't know.

No Reward for the playtester (outside of a credit).

Run by someone other than you and you are nowhere around.

That way, you get truly unbiased opinion. Heck, sealing the reviews/remarks in envelopes unsigned isn't a bad idea either.

Sounds like you are ready, so good luck in the search for manufacturers... stay with experienced game manufacturers, or you risk roll the dice.