Gardyloo

Well, the deal with Seward and Whittier is that you travel on the same highway to get to both. The turnoff (from the Seward Highway) to Whittier is around an hour from Anchorage, then you travel 10 miles up Portage Valley to a one-way train/car tunnel that's only open a few times daily in each direction, which will take you into Whittier.

To get to Seward from Anchorage, you take the same highway, but don't turn off at Portage. That drive is around 2 to 2 1/2 hours, i.e. roughly twice as far as the Portage turnoff, or, put another way, an hour and a bit farther down the road. If you do separate day trips to Whittier and Seward, you're basically driving the Turnagain Arm part of the Seward Highway four times. Now it's very scenic and all that, but, assuming you're visiting in the summer, it's also very prone to slow-moving traffic, and following an RV or a camper for hours up the Seward Highway is a really irritating common occurrence.

I get the point about hotel points, and, again, assuming you're coming in the summer, you won't have any daylight issues to prevent your basic plan. However, if you spent a night in Seward, you could take one of the Kenai Fjords National Park cruises that operate from there (very different from the glacier cruises out of Whittier). These would be difficult to do with a day trip, unless you left Anchorage at oh twilight thirty.