I'm a moderately regular flyer, primarily domestic US though more than a few international trips under my belt. I know enough to get in trouble, but not quite enough to keep all the posts I've spent the last hour researching completely clear, it would seem...

Regardless, I'm going to be flying First for the first time back to the US from London. For the long-haul portion, my options are to fly a 747 to IAH or 777 to EWR.

My main question is, are there noticeable differences between the first class seats/cabins on the 747 vs the 777?

From my research, it seems it will depend on which *specific* 747 or 777 I am eventually destined to get, which won't be available until 72 hours before the flight? If that is correct, are there better odds of having a better product on one or the other (if there is any difference)? Or are the odds better for a particular route (to the NYC area, for example)? Or am I making this harder than it needs to be and I should just be picking what flight times work marginally better than the others?