Suppose you want to enter the market immediately. Then you have two choices, marketable limit orders and market orders. Which one do you prefer? I don't see any advantages of marketable limit orders because they may not get a fill immediately.
If you mean for US equities, the difference with the limit order is this: you don't run the risk of getting blindsided by a sudden vanishing of the ask and thereby getting filled at a stub quote (e.g., paying $199,999 per share for a $10 stock) and end up having to hope/beg for a bust from the exchange. I always use a limit for equities, and I don't think it's ever caused me to "not get a fill immediately" when I was aiming to buy at the ask/sell at the bid. The only situation in which it would (at least during regular hours), would be one in which the price moved against you between the time you saw the quote and placed the order -- potentially so much out of your favor that you wouldn't want it anyway (e.g. at $199999). But you can always set a limit beyond the present bid or ask if that's a big concern.
+1. as volume getting lower and lower every day ,spreads are getting higher and higher. it is now not uncommon to see 1-2-4% spreads on fairly liquid stocks thru regular trading session. it is up to you,if you want buy it at market. just keep in mind that you will be subject to a mini flash crash every time. that is-if there is not enough orders on that side-'they' can and will cancel their orders BEFORE your market order can hit it. and as Occam pointed out-if you submit market order -you are automatically accepting ANY price. good luck with that. from amount of questions\new threads about very basic things you been asking i can assume that OP have no knowledge of the subject. i would suggest you to open either demo or paper account and spend few days playing with it. then read a book about micro structure.. you will find the answers on at least half of your questions. save us some time
Thanks! Should I use stop limit orders for protective stops, instead of stop orders, too? Once stop orders are triggered, they will be exposed to the same risk as market orders. If so, how do you balance the risk between holding your position you want to close for too long and suffering huge slippage?