This discussion may contain spoilers!
So, I am playing this series again on my new computer. With Episode 3 (if you didn't save Lilly) you kept the RV and you would drive to Savannah. But, since you come across the train and realize that its tracks lead to Savannah, you use the train anyway. I think that it would be smarter to just move the train, and continue with the RV. What the group should have done was simply move the train out of the way, stop it, and then continue on with the RV. They should have done this because the RV makes virtually no noise compared to the train, and although the RV has barely any miles left in her (Kenny says it is about to die), they probably still could have made it to Savannah.
This would change everything because there would be no horde in Episode 5. The horde not being there changes many things.
First, Vernon most likely would not have stolen the boat because he would not have seen the horde in the bell tower at the end of Episode 4. This means that the group would have been able to get to the ocean after they got back Clementine. Another interesting thing about this is that Vernon would not have suggested to take Clementine. Vernon was hinting that his group would be safer than Lee's group by telling Lee that Clementine would definitely be safer than him. Vernon said this because he was going to steal the boat to get his group away from the horde. This means that Lee would not have suspected Vernon to have taken Clementine, and they would never end up being at the Hospital, stuck on the roof, which would save them time. Lee would have been bitten no matter what, but Clementine would have been safe on the ocean with the rest.
Second, the group would have never had to travel by roof. They could have just walked on the streets to get to the Marsh House. This is important because Ben (if saved in Episode 4) would not have fallen and would not have been impaled. So he would still be alive, and Kenny would not have been regretful towards Ben and basically kill himself. That means that Ben and Kenny would both still be alive/with the group to save Clementine.
Third, if you didn't save Ben in Episode 4, Kenny would sacrifice himself to get the walky talky out of the hole. This would not have happened if the horde wasn't there because they would never be on the roof in the first place. Kenny would not have to jump down to get the radio, and he would still be with the group.
Fourth, Lee would never be alone when he went to the Marsh House. Lee would have no need to cross the street by going across the sign. He would have never been separated from the rest of the group from the above differences, and this means that the group would have numbers over the Stranger, and they would immediately be able to get Clementine back.
Fifth, Omid and Christa would never be in the group. This actually would most likely not really change anything in the story because the were not too important in the main story line. Kenny may have not jumped down to get the radio so stupidly, but in the end, it wouldn't change too much. So in the end, Lee would still be bit because he was bit before the horde arrived. However, everything else would be so much different. The ending would most likely be Kenny, Ben (if you saved him), Molly (she would maybe stay because there would be enough room on the boat [and if you saved her at Crawford]) and Clementine all getting on the boat to get to the ocean. THIS IS ALL CHANGED JUST BECAUSE THEY USED THE RV INSTEAD OF THE TRAIN.
You could also say that they could also have used the train. But instead when they got to Savannah, they sent it back where they came from to make the horde follow the train going the opposite way from Savannah. This would only have all the above differences, but instead Omid and Christa would be in the group (but it would not change much.)
I thought that this was a really cool idea because it turns out that it would have most likely changed the story a lot.
**I always love to hear what other people think! **:D