I think toe-up is easier.
Cuff-down socks involve short rows, picking up stitches along a selvage edge, and the Kitchener stitch. The heel is worked differently from the toe. And there is always the fear that you made the cuff too long and will run out of yarn before you finish the foot.
Toe-up socks just involve short rows. The heel is the same as the toe (if your pattern uses a provisional cast on and the toe is worked with short rows). Since you knit the foot first, you know that you have enough yarn and can make the cuff as long as you want. Plus, you can try it on as you go if you use magic loop.