I've gone through stages of pants wearing - learning lessons along the way. I'll share my thoughts but decide for yourself.
Cargo pants. I used to like cargo pants but as I traveled lighter I found I carried less and didn't need the pockets. Cargo pants went off the pack list.
Cotton in general. Cotton won't keep you warm if it gets wet and it dries very slowly. I had a pair of cotton Columbia cargo pants one trip. The first time I tried to hand wash them and line dry, they stretched out so much they were worthless. I finished the trip in a cheap synthetic pair of cargo pants I bought somewhere like a Walmart.
Jeans. Jeans will make you fit in because everyone wears them in Europe. That said, not all jeans are created equal and Europeans care more about fit than most Americans. Our baggy, sagging jeans don't make you look European. Jeans do stretch out in the waste, butt and knees and won't shrink until they are machine washed and over-dried in a dryer. Jeans, like other cotton, won't keep you warm when wet.
Fit. Europeans don't necessarily wear skinny jeans but they do like their clothes to fit. You won't see saggy crotches or baggy clothes in Europe on most adults. I now pay a lot more attention to fit when I shop for clothes.
Pockets. Once I went to a more fitted pant, stuff started going in pockets on my jacket. I'll usually put a debit and/or credit card in one front pocket and some paper bills in the other. The backup cards, cash, passport, etc. go in a neck wallet worn over my head and one arm and kept on the side under my shirt. I may put a phone in the back pocket but I'll keep it in hand when the crowds get thicker.
Packing. When (not if) you decide to pack light, the weight and bulk of your pants will make a difference. The heaviest and bulkiest are jeans and cargo pants. I now pack to keep things light and easy to pack (and wash). If you want jeans, you can find lighter weight jeans that won't take up near as much room as their thicker cousins.
Favorites now? I was really a fan of golf pants (specifically Adidas pants) because they are so light and wrinkle free. They take up little room or weight in my bag and wash and dry amazingly quickly. Recently I bought some stretchy synthetic pants that resemble a light jean. Two companies sell pants that are virtually identical (one is Eddie Bauer). They're nearly as light as the Adidas. They've added a second zip close back pocket, deep enough for my smart phone, that I like.