This is just an opinion, but why do I feel like the most of the 4.6 votes are from owners that have never played in leagues outside of the MFN. If so, of course they will pick the former option to limit cheats, I might or might not blame on punt block exploiters in MFN. In leagues run by a player admin, they will commonly use rules to forbid or limit these exploiters (I'm looking also at weight exploiters).
In a league ran by a 4.5 engine, specifically in the GM Football League, take the best offensive team this year in the CJ's Ravens. They had a QB throwing 50 TDs, and a RB who ran and caught each for over 1,000 yards. That shows how good the 4.5 sim engine can be. While the passing numbers are strong this very season in that particular league, there are players who ran over 1,500 yards and players who caught for over 1,500 yards.
In the 4.6 version, you can't even get 3,500 yards which is a common feat in the NFL. You rarely get a QB throwing over 25 TDs in a season, again common feat. The YPA is just putrid, with nearly no one reaching 7.0 YPA, which is again a common feat in the NFL where 14 of the starting NFL QBs last year had 7.0 or over.
In the NFL, only two teams will run the football as much as the 4.6 to get points, that is the Ravens and Derrick Henry. Don't forget the Titans were super good in the deep passing game which will never happen in 4.6 and Lamar Jackson is just Lamar. There is only a trend up for passing the football since the invention of the forward pass. Not only is it more effective than the three run and punt, it also gathers realistic and favorable action to the game.
I enjoy passing the football in my leagues and rarely do I run the football a lot. In 4.5, when the passing game is used more, you get better offensively. In 4.6, when the running game is used more, you get better offensively. So in 4.5, passing the football has a higher percentage than in 4.6 where running the football is used much more often.
Here in a website, it tells the play selection percentages of the NFL in 2020.
https://www.teamrankings.com/nfl/stat/passing-play-pct?date=2021-02-08 Notice how only 3 teams dipped below 50% of passing of football? Guess who was leading the way... Derrick Henry for the Titans, Cam Newton for the Patriots (who has since passed more this season with Mac Jones), and Lamar Jackson for the Ravens.
Again this is just my opinion, but based on the facts above. 4.5 statistically wise is too strong on the offense and weak on defense while 4.6 statistically wise is too weak on the offense and too strong on defense. I would not update to 4.6 since it would be better to have a good offense like the NFL rather than a good defense. We wouldn't want to go back to the old gritty 70s, do we? No! Of course not, we would rather be modernized in the 2020s. Honestly, if we get something like a 4.55, it would be the best of all of us.