It depends if you're talking about the medium (coax vs. twisted pair) or the typical interface card using that medium. Typical small coax interface cards of several years back were 10 megabits/sec, using BNC connectors on RG-58 coax. Typical twisted pair interface cards (of today) are capable of 10/100/1000 megabits/sec depending on the quality of the cable. In terms of timeline, coax came first and then twisted pair. At one time the interface cards available were roughly equal in bandwidth at 10 Mbps. The 16 Mbps you see was (probably) for a different technology (not ethernet based) known as Token-Ring, sponsored by IBM. Token Ring was initially 4 Mbps but eventually an upgrade to 16 was developed. T-R ran over STP (Shielded Twisted Pair) as opposed to TP. Eventually token ring pretty much died out due to the significantly increased cost of the STP installation and the significantly greater price of the interface cards which ran $150 at a time when you could get a twisted pair ethernet for $50.
If you're talking strictly about how fast you can push bits thru the media then Ignacio is right, both are capable of gigabit speeds. Note that both have substantial limits in terms of the max distance they can go at super high speed. If you really want maximum speed and distance - you want fiber optics.
1That is a terrible, terrible article. – Ignacio Vazquez-Abrams – 2010-11-06T11:33:46.483