So I am in Lisbon at the moment and one of the reason is for the egg tarts, I must have had about 8 in the last 2 days.
Today I went to the 2 favourites, one being labeled by many as the best, Pasties de Belem (just 1 location) so I did a little side by side taste taste with another one in the city which has a couple of places in town.
Ignore the burnt top on the Menteigaria, you can't taste the burnt and its not all of them. But appearance wise, at this on these 2, the Belem one looks nicer.
First thing I noticed was the Belem tart has a slightly flakier crust at the bottom, it has more layers. Both are ultra crispy, that is one thing about egg tarts here, all the ones I've tried in the UK and even the ones in Macau (the KFC one...there is a story there), I don't recall being like this. I got to say the Belem one has a better bottom crust. Both are crispy but Belem crust has more air in it. Menteigaria might be for you if you prefer a marginally thinner crust. VERY close call.
The egg tart content itself, they have the same consistency, sweet, just about staying together when you bite into it and gooey. I love it. Menteigaria is a fraction sweeter than the Belem. If I weren't eating them side by side then it would be hard to tell.
I have to say because of the crust, Belem wins it by a hair in this head to head, but the problem is that it is also 5 miles out of the city, a good hour away on the metro or a 90min walk (which I did) to get them. If I were living here, I wouldn't go there just for it because honestly, the next batch, Menteigaria tarts might have the same flaky crust at the bottom if it weren't as burnt in this one, who knows. They are both excellent, certainly can't get them this good in the UK.
To prove that it is not always burnt, I took this photo from TimeOut Market's Menteigaria stand.
I also went to another store where they were making it right in front of me and it was too hot to eat.