While we liked West to East, if it looks like the passes will be snowed in, you might consider going East to West. The weather is likely to be a lot more comfortable that way.

We liked the West to East route for a few reasons. These included the following:
1. Getting air travel out of the way up front when we could plan the date more easily.
2. Being far away in the beginning of the trip minimizes any desire to back out.
3. Seeing new territory right away.
4. Having a good welcome home at Yorktown more near family and friends.
5. Saving the hardest climbs for late in the trip.

I guess we liked it better for just about everything except the sun in our eyes in the morning and the less comfortable weather.

I think that if I had to leave in May, I would wait until the last minute to buy tickets and be prepared to start in the East if the passes were still badly snowed in.

As far as the sleeping bag... I went with a 30 bag and was OK, but we had abnormally warm weather most of the way. Also we had to do an extra long day to get to lower altitude at one point to keep from freezing. Leaving in May I would be inclined to either take a 20 degree bag or to take layers of clothing that could be worn in the bag.

BTW: We sent stuff like cold weather gear home and had warmer weather stuff sent to us via general delivery. That is a help in being able to adjust the load to the conditions as you go.

Another BTW: We didn't find the prevailing winds thing to actually pan out to be an advantage. In Wyoming we had bad headwinds. and in Eastern Colorado and Kansas there was a side wind that was more in our faces than in our backs. Getting an early start was a big help with this because the winds didn't usually kick up until later in the day.