In most things, yes. However the 465/9s accelerate quicker which allows them to run to time on the Chatham Main Line despite 90mph speed limits. I'm not saying 377s are bad at accelerating. They are actually still quite good. It's just that 465/9s are better.
And then remember, most 377 combinations I have seen are 7/8/11/12 coaches which restricts acceleration. Whereas the 465/9 I timed at 43 seconds to 54mph was a 10-car (2 465/9s and 1 466) and yet was unaffected. So there's that factor too.
However 377s are definitely more "the train of the future" than the 465s.
Southeastern has:
- 25x4-car 377/1/5s
- 68x4-car 375/6/7/8s
- 34x4-car 375/9s
- 10x3-car 375/3s
Bearing in mind that 4 375/3s are used all day on the Sheerness and Medway Valley Lines (5 in the peak), this leaves essentially 4-6 3-car units to make "unusual" formations:
- 6: 3/3
- 7: 3/4
- 9: 3/3/3
- 10: 3/3/4
- 11: 3/4/4
- 12: 3/3/3/3 OR 4/4/4
SE 375s and 377s don't work in multiple with each other, even though the two are effectively technically homogeneous. However, 375s do serve the Maid E line, I have seen them! (If you're wondering, my profile picture is 377164 at Barming, with 377508 trailing)
Southern has:
- 29x3-car 377/3s (28 ex-375/3s and 1 ex-377/4)
- 34x5-car 377/6/7s
Thus facilitating easier 6/7/9/10/11 car formations as they have a much larger and flexible fleet.
Finally, let us not forget that 465s are the fastest accelerating DC EMU in the UK, so they always win that over the Electrostars.