Coming from Apple AirPods Pro 2, I will inevitably compare them since their price is about the same. Here’s what I have to say:
The noise cancellation function is worse compared to that of the AirPods.
In terms of fit in the ears, the Sennheiser are better, though this may be subjective depending on each person’s ears.
As for build quality, I can say I was disappointed as it seems to be much inferior to that of the AirPods and in no way is it of the 200€+ class. The plastics feel very cheap and not to mention the magnet that closes the case, which feels like it was taken from a fridge magnet.
In terms of sound quality, I consider the Sennheiser to be top-notch and this is their strong point. Very balanced sound and just right in all frequencies without exaggeration. The app also helps here, where you can adjust the sound to your liking, something the AirPods lack.
The battery life is longer on the Sennheiser.
As for the microphone, the AirPods are superior. The person you’re talking to hears you more clearly with less interference than with the Sennheiser.
Their button controls are easier and more straightforward on the Sennheiser than on the AirPods.
In conclusion, my opinion is that the only reason to choose the Sennheiser over the AirPods Pro 2 or other similar earbuds is if you listen to music and care about sound quality. In no other important area do they dominate.

Pros:
+ Very good sound both in the lows, as well as the mids and highs. Good bass. Ideal headphones for listening to music.
+ Very good battery life
+ Support for multi point connection so they can be connected simultaneously to both my phone and my computer.
+ Quality construction. I have had them for 1.5 years and they have not shown any problems, unlike the 3rd generation ones which Sennheiser replaced for free with the 4th!

Cons:
- I wouldn't get them for the gym since their fit is good but not excellent. There are other headphones that are made for listening to music while exercising.
- For those whose number one criterion is not sound quality when playing music, but are mainly interested in microphone sound quality during phone calls or ANC, there are headphones that perform better in these two areas.

Conclusion:
Ideal for those who care above all about sound quality when listening to music at home. On the contrary, not ideal for those who want them for listening to music at the gym or for those who put great emphasis on ANC or the microphone during phone calls.

Coming from the Momentum TW2 to the Momentum TW3 and now to the Momentum TW4, we have the following in comparison to the Momentum TW3:
- Slightly better battery (30 minutes more battery life - now 7.30 hours of autonomy),
- Slightly faster charging and the case now has 30 hours of autonomy instead of 28 hours,
- With the latest firmware update, the 4s have bt 5.3 compared to 5.2 (the difference with an iPad Pro 2022 device that supports protocol 5.3 is noticeable in terms of interference, especially when you move away and have walls in between),
- Slightly clearer and louder sound (in volume) compared to the 3.
On the negative side:
- After two years from the 3, I would expect something better in all areas (since at the release date they are more expensive than the 3 - the 3s were found on sale and purchased during Black Friday for €204),
- Just like the Momentum TW2 that were replaced under warranty with the Momentum TW3, they had issues and stopped working without any signs of misuse, and it remains to be seen if these will last as well.
In conclusion, if you have the 3, it’s not worth upgrading to the 4, better to wait another two years for the 5s to see if they are worth it.

In terms of sound, it’s the best. In terms of calls so the other line can hear you, it’s as if Sennheiser wanted to make them terrible. I had returned them because I thought it was a technical issue, but unfortunately it’s the model. Also, the ear tips are made from such bad material that after 1 to 2 hours your ear stings and you have to get other tips, e.g., memory foam. Unfortunately, I’m quite disappointed even though, as I said before, the sound is amazing.
Another negative for this company is the customer service. It’s like talking to the Greek Post Office, I don’t need to say more. On the positive side, the noise cancellation is so good you can’t even hear your own breath, really great job in this area.
In conclusion, when a customer gives you 200 plus euros for headphones, they don’t expect them to make coffee and breakfast at 10 in the morning, but at least the basics: to work properly and not raise your blood pressure.
edit: Guys, the microphone quality is atrocious, you need a strong stomach—no one can hear me, wasted money...

Coming from the Momentum TW3 compared to the new TW4, I have the following to say:

The sound remains excellent with no major differences. The new TW4 supports the additional aptX Lossless protocol which has native uncompressed CD-quality sound, but very few phones support it, so I stuck with the very good aptX Adaptive.

Regarding sound quality, I will say what almost everyone says: they are simply amazing, especially when you easily adjust them to your liking through the Sennheiser app. Endless bass, tight, top-notch vocals, and detailed highs. A delight on Tidal Max! What impressed me (and from the previous model) is how dynamic their sound is and the complete absence of distortion no matter how much I pushed them in volume (and they have a lot)!

I consider the ANC to be about 10% better - not a big difference but they definitely offer a bit more quietness.

The Transparency mode remains quite good and felt the same to me, although I have the impression that the wind is less bothersome now.

There is an upgrade in Bluetooth which is now version 5.4 and they also support the new Auracast, allowing countless headphones to connect to a transmitter. However, neither of these upgrades has any impact on how I listened to music until now compared to the TW3.

I find the option to charge up to 80% very good so that the battery is less stressed for greater longevity (I do the same with my Lenovo laptop).

The shape and size of the headphones and case have remained identical to those of the TW3.

In conclusion, they remain one of the top true wireless headphones you can buy. If you are looking for quality sound and features (and your budget allows it), get them with your eyes closed! However, if you own the TW3, I don't see a significant reason to upgrade since, apart from minor improvements in certain areas, their sound is almost the same.