City on Monday announced Losada had signed for them on a two-year contract after leaving Barca, who won the Champions League last term as part of a treble.
The Catalan outfit's European campaign included getting past City in the quarter-finals, winning the first leg 3-0 before losing the second 2-1, and thumping Chelsea 4-0 in the final.
Losada told a press conference on Tuesday: "I think Man City was the best team we played against this year.
"I just had the feeling, being honest, the first game they were a bit respecting us too much, because I know Barca were showing very good football.
"But they definitely showed the kind of team they are in the second leg, and for me it was the perfect team to join after last season."
Losada, who was Barcelona captain, made 375 appearances for the club across different spells after coming through their youth set-up, and helped them win multiple honours, including six Spanish league titles.
The 30-year-old Spain international is returning to the Women's Super League having previously played in the division for Arsenal in 2015 and 2016.
She heads to City with Gareth Taylor's side having finished two points behind champions Chelsea as runners-up last season in the WSL, which the club last won in 2016.
Losada said: "It (leaving Barca) was very tough for me, but I was thinking about it for months and in the end winning the Champions League made things easier for me to decide in the end to join Manchester City.
"The reasons I picked Man City - of course it is a big team, I want keep playing big games, Champions League.
"I know they haven't won the league trophy for the last five years and I think I can help them a lot. It is a new adventure for me, I'm very ambitious and I'm looking forward to it.
"The English league is very competitive. You have Chelsea, which show for me a completely different kind of game, a transition game with players really quick. I think the English league is the most tough one.
"But I have seen Manchester City playing and it reminds me of four years ago when I was playing for Barca. I think every year they are better and hopefully football gives us chances this year to fight for trophies.
"When I went to Arsenal I was very young, with not even half of the experience I have now. I think the English league really suits me now, plus my experience, I think I can bring Man City a lot of new things to be successful.
"I think probably that (the WSL) is the first priority, but playing Champions League, they are massive games where you can show the team who you are, and they are the games that make you better in the future."
Regarding the prospect of facing Arsenal, with whom Losada won the FA Cup and League Cup, she said: "I think it's going to be definitely special, and a bit weird because I felt very comfortable, especially (with) all the love the fans showed me.
"But you know, football is like this - now I'm playing for Man City.
"I just want to say thankyou to all the Gunners, because they've always been very good to me."