SFR will be the easiest to flip. Just think about your market pool. What kind of people buy SFRs? Everyone. What kind people buy multi-units? Only investors with the occasional owner occupant duplex buyer.
So, now that you know what market you want to cater to (everyone), now your decision is controlled by how much money you have to work with. You make a deal work in any neighborhood if the numbers are right. So it is best to invest in the market in which you are most familiar. If you know the 100K to 200K market like that back of your hand but only have minimal experience in less than 50K or more than 500K, then you stick with what you know.
I recommend becoming completetly familiar with the type of property YOU feel most comfortable with and start getting to know some wholesalers to see what they offer and how it compares to retail and REOs(sometimes there's not a lot of difference.
Then I would deploy wholesaler strategies to find deep discounted properties without paying the middleman fee. If you get a property at a deep enough discount, any exit strategy will be a winner. Then your exit strategy will then be determined by your goals rather than current market conditions.
Take this with a grain of salt as I have only recently acquired and rehabbed and operating my first buy and hold property. But after buying said property from a wholesaler, I can tell you that the above advice is exacly what I will be doing when I have enough cash reserve to do another deal.
I am a fan of buy and hold. But I have a day job...