TBH your experience is going to vary wildly depending on the specific person you're working with, regardless of whether it's ACS or 3rd party, so my best advice is to make sure you talk to the actual consultant who is actually going to be working with you on a day-to-day basis before you fully commit/sign anything, and maybe even bake that into the contract so you can back out if they pull the old switcheroo. NOT some sales person, partner, manager, director, account rep, or any of those people, regardless of how many promises they make, because they're not who is actually going to be helping you. That being said, I generally opt for 3rd party services because it's usually on an hourly basis (so you only get charged for what you actually use) versus ACS which is typically billed on a recurring monthly basis (even if you don't use all the hours, and then they charge you more if you go over). It's not like NetSuite has any special sauce that makes them way better than 3rd party, but the inverse is also true.