Nadeem has the back-twister technique, Neeraj has the forward momentum fallover technique. This means that you will see at point of release, Nadeem rotates his back a lot more, while Neeraj does the top-of-toe release, with foward momentum usually making him fall over.
There are pros and cons to both techniques : the back-twister technique lets you get closer to the foul line when releasing, while the fall-over technique you are always 1-1.5m behind the foul line at release, since you need space to fall over and not foul.
However, the fallover technique is a lot more consistent and less injury prone than the back-twister technique, is why its the most common technique in the field. When you rely on back-twister technique, you end up with disc damage over time as that is a lot of tortion force on the spine, the one type of force the spine is the worst at dealing with.
Also, the back-twister technique uses less body momentum but far more core muscle & upper body strength, which means, there is bigger variance in your best day and worst day performance ( as you rely less on nearly constant momentum force).
This is why Neeraj i think will be a bigger threat in javelin competitions than Arshad, unless Arshad really is that much stronger and has unlocked some secret to holding the javelin to regularly break 90m mark.
PBs matter less in javelin/hammer/discuss/shot-put etc type of throwing sports than what your average throw is.
Because even the best javelin throwers end up with 7-8m difference between their season's best and season's worst competitive throws.
Neeraj is dominant in the sport because he almost never misses the 85m mark in medal rounds of where he participates. In fact, going all the way to 2017, which is like 7 years, the dude has hit below 85m in medal round only once. Ie, a 9-1 record in last 10 major events for throwing 85m+.
No other javeliner has even done this 5 times in the same time period,fyi. (Arshad Nadeem is that guy, fyi).
Basically, Neeraj is the djokovic of the javelin field. You know that if he is present, you will have to go 85m+, most likely 86m+ to win. Day in, day out, thats not an easy task, Because if you are having an off day ( slightest of niggles etc), you can easily drop down in the low 80s ( 81-84m mark) in javelin.
Which means that he is always the guy to beat in the last few events he's played and he will remain so, unless age or fitness changes. And that is why, he is by far the most winning javelliner since 2018. Thats six years and counting, for anyone keeping score.
Yes, he got ' out-feded' in this Olympics. Happens. But reality is, day in-day out, he is the only one who's gonna be in #1-#2 spot in the field and onus is on YOU to match him that day and some days you will match him, but over time, he will win more than anyone else and so far, he has in the period he's been top quality.