The data which I will be using is a collection of ~60k games played on Patch 4.19 (Season 4) and Patch 4.21 (Pre-Season5 / Season 5). All of these games are played by Diamond and up players on the NA server. I chose 4.21 instead of 4.20 due to some very significant changes (especially on dragon) that were introduced on 4.21.
Win Rate For Teams That Takes The First Objective
First let's look at the win rate for teams that takes the first objectives. There were a reddit post a while ago that talks about the win rate for teams that get the first dragon, but it wasn't very clear if it was Season 4 or 5. Using my data I get the following:
|The Team that Gets:||4.19||4.21|
|Number of Games||12816||49095|
As you can see, the win rate for the team that gets first dragon did not really change too much from 4.19 to 4.21. As a matter of fact, none of the "First X" win rates changed too much except First Baron (two-sided proportion tests with a significant level of 0.05 and Bonferroni correction yield no statistical significance). It's difficult to say if this is the intended result by Riot, but further analysis could shred more light onto the matter.
Let's also look at gold - in particular, gold lead and win rate. During the two ESL Tournaments that were played on Patch 4.20, casters during ESL has repeatedly said that gold lead does not matter as much in Season 5 due to the Dragon changes. Is this actually true for solo queue for Diamond+ players? The answer seems to be "no".
|Gold Differential @ 10th min||4.19||4.21|
|0 - 500|
|500 - 1000||60.65%||61.93%|
|1000 - 2000||70.83%||71.81%|
|2000 - 5000||85.15%||85.97%|
|5000 - ∞||96.20%||98.42%|
|Gold Differential @ 19th min||4.19||4.21|
|0 - 500||51.87%||51.96%|
|500 - 1000||53.65%||57.04%|
|1000 - 2000||61.17%||63.23%|
|2000 - 5000||74.87%||77.70%|
|5000 - ∞||94.56%||95.08%|
Here, we see that with the same amount of gold lead, the team that is ahead in gold actually wins more often in 4.21. For example, a team that is leading in gold by 2000 - 5000 at 19th minute wins 74.87% of the time on 4.19 and 77.70% of the time on 4.21. In other words, there is evidence that gold differential has become MORE important with the new season, not less.
My theory is that with the Dragon no longer providing gold, it's harder to actually get a gold lead. Consequently, once you do get a gold lead, it is actually a lot more valuable. It is also possible that the team that leads in gold gets more dragons and vice-versa. Overall, if we look strictly at gold lead, it seems to be more significant in Season 5.