Which is the best, the up & coming USB 3.0, or the combo USB 2.0/eSATA port?
That is too general a question and is like asking which is better; coffee or a milk shake? They are both drinks but don't necessarily serve the same purpose - or meet the desires or needs of all people.
USB3.0, as its name implies, is a "universal" I/O used to support many devices; external drives, printers, card readers, cameras, keyboards, mice, PDAs, Bluetooth adapters and many more - but not disk drives! USB3.0 is superior and backward compatible to USB2.0 and USB1.x. It will "toggle down" to 2.0 speeds, but 2.0 cannot "toggle up" to 3.0's. USB3.0
has superseded 2.0. It is not "up & coming". It's here! Has been for over a year. Perhaps you need to look at more current notebook offerings. If a new notebook, computer, or motherboard does not support USB3.0, it is not a current design.
SATA is the current standard for
drive interfaces for today's "wintel" computers - superseding EIDE. Nothing "universal" about it.
USB and eSATA are just two of many data interfaces used in today's computers. Until Western Digital and Seagate and the optical makers start making drives with integrated USB connections, you will need both USB and eSATA, if you intend to use both USB and SATA devices externally. I don't see that happening. I think light will come to motherboards first, requiring a whole new I/O, possibly superseding both USB and eSATA eventually. In any event, buying strategically is almost always wiser and better on the budget. USB3.0 is the current standard. USB2.0 devices are phasing out, being replaced with faster 3.0 versions. To take advantage of USB3.0's enhanced performance, both sides of the cable must be 3.0. So why buy a
new interface that has already been superseded? What happens in 6 months when a new external device you want is 3.0? Do you live within 2.0 performance limitations, or plop down even more money for the 3.0 interface you should have bought in the first place?
Buying a USB 2.0 camera or keyboard may be fine - they don't need the speed. But interfaces are something that will affect performance of everything connected to it, for the life of the product. USB2.0 device prices are pretty attractive for a reason - they are obsolete. Strategically spending a little extra today for today's technologies is cheaper in the long run and will carry you into the future, not hold you back in the past.