Hi Ken, welcome to the forums.
I just removed your other post in the same forum asking which is the best brand after discovering that you also posted this one, which effectively deals with the question of what controller to get as well. While we don’t mind answering questions we prefer them with a better background, like this one and in one post, not two.
Back to this post.
I’d say you are about a year (or two) away from using Flip. You are probably also a while away from playing weddings, imho. Weddings have singular character that other gigs don’t have, they are essentially one-off’s. No do-overs. While well paid gigs, the require you to have all your gear in tiptop shape (not just your controller, but everything) and they require you to be able to do the party justice. This only comes with a nice fat chunk of experience and skills. Weddings are no training ground. Things you can get away with at a venue, a birthday party or a corporate event, can ruin a wedding, a couples “best day ever”. And trust me, you don’t want to be in those shoes. Not saying you shouldn’t aspire to be a great wedding DJ, but it is, in my book, the one type of gig you need to be at the top of your game, a true pro.
Mixdeck Quad and DDJ-SX are such totally different controllers, that if you are considering both, you have clearly not figured out what you need yet. There is no set of wishes/demands you can put towards a controller choice that will get these two as your shortlist.
Personally I have never been interested in a unit with built-in CD-players (USB sticks makes sense perhaps, but CDs not really). Since I do run into CDs still on occassion at (indeed) weddings and other events, I have two seperate CD players next to my controller which double as backup players with their USB stick capability, should my laptop go south.
For the same reason I have a controller that doubles as a standalone mixer. And one that has 4 channels instead of two. While currently using the DDJ-SX as a result of equipment swap, I’ll be returning to what I think is the best mobile DJs controller, the Denon MC6000mk2. But again, that is just my personal choice.
Write down what you feel you must have and would like to have. Then go through the controller guide. Then try to get some hands-on with your favorite two controllers within your budget. Only then decide.