There are many ways that both WA and Telegram can be subverted/backdoored/messed up. What it really comes down to, is who do you trust? Do you trust WA or Telegram? Personally, I trust WA a lot more than Telegram since WA has Moxie on their team and Telegram says, "Trust us" and a very unreasonable security challenge. I naturally don't trust people that say "Trust us" and put up unreasonable security challenges.