Both Toby and Markxxx had some good comments about this.
Had the Vietnam war occured today, with the modern newsgathering technology we now have, chances are it would have taken up even more airtime on the broadcast networks' evening newscasts. We'd probably have at least one live battlefield report every night on the evening news ("We're live in Da Nang, where it is already mid-morning on Monday, and as you can see Walter, American troops and the Viet Cong are in a fierce fire-fight for control of this city...").
And the cable news channels would also have devoted lots of hours of coverage.
On the other hand, had the Iraq war occured in the late 1960's or early 1970's, there probably would have been less TV coverage because film would have had to have been taken out of the battle zone and flown to Tel Aviv, Athens, or London to be fed by satellite to the 'States, much like Vietnam batlefield footage was flown to Tokyo to be uplinked to a satellite to be fed back home. In either case, film would be at least 24 hours old by the time it was shown on the evening newscasts.
Vietnam and Iraq are different wars in different eras as regards newsgathering technology. The only way TV coverage of these two wars can be compared would be to look at what television news technology was available then and what is available now and to guess as to how the available technology would have affected how war could have been covered then compared to how it is covered now.