Whatsapp's web client is just an UI to the mobile app meaning you also need to have phone connected to internet always for it to work.
Telegram is much more responsive compared to the Whatsapp.
umm... citation needed?
There's an open $200k bounty for years now. Some "expert in the field" (who just happens to work for not one but two competitors -- yes, I'm looking at you, /u/moxie) posted a blog post right afterwards, about a competition not being the same as a proper design / security audit, and that's correct. But I've seen people try and fail over the years: the crypto holds. Moxie and co would have loved to see it fall too much not to have had a stab at it, never mind the bounty, but apparently they failed.
I think the e2e in Telegram is solid. If you're really paranoid about some file in particular, you can always send an encrypted zip or GPG encrypt it -- I'd recommend that anyway, since otherwise your chat's encryption keys (which are in use all the time, thus quite easy to get at) also unlock that sensitive file.
> For non-phone related use I'd go for Wire https://wire.com/en/ encryption wise.
I would recommend Wire.com too. This needs more awareness, since it does everything we've ever wanted, has the protocol everyone seems to support, is open source, works on all popular platforms, etc. Except nobody uses it, so the network effect is not there :(
I'm a Telegram user (because network effects) and I agree it's a fast, slick app with both good mobile app and web interface, but I do not expect it to be secure.
Depends on your standards and your use-case. If you message from your phone most of the time, you can open an encrypted chat[1] with someone and it's properly encrypted.
If you use desktop too a lot, then this doesn't work because the desktop client doesn't support end to end encryption. In that case, you're at the mercy of them not reading your messages. Pretty much the same as with WhatsApp (closed source), Facebook messages, and virtually every other chat application out there.
(Except Wire.com, by the way: they're really cool but nobody uses it, so no network effect there unfortunately. I wish I had a good reason to get people off of Telegram except for "maybe some sysadmin is laughing at your jokes too".)
[1] the application calls it a "secret chat", and recommends people not to use the terminology encrypted chat "because all their chats are encrypted" (yeah just like https: until they're in your datacenter, no matter what they claim). So I'll use the proper term instead of the marketing term: encrypted chat.