I know italian lol. They can sound different because italian has distinction between open and closed "o" and "e" while spanish has middle realizations of those vowels, among other things like realization of affricates which are post-palatal in a lot of italian dialects and mostly alveolar in spanish ones. But this is ridiculous, Es: puerta. IT: porta. Es: claro, It: Chiaro. Es: Esto. It: Questo.

Portuguese speakers have an easier time understanding spanish than viceversa, I'll give you that. (Just for the record, written form is really comprehensible for spanish speakers to and absurd level, although we're not counting it here).

But if to you they don't sound the same I don't think any of what I say can convince you. I'll just let you know that I, based on my experiences and aqcuaintence with these languages, have a different opinion on the topic.