Both liquids (as many people said here that liquids are worse for smell and mold problems)
Brazilians are big fans of strong scents. Just like mexican "mamacitas". People tend to use much more than the recommended dose. Actually, Brazilian washers tend to have a huge softener dispenser because we understand that the consumers like to use much more than the regular "1 cap".
With the concentrated products, manufacturers simply found the golden egg chicken. the regular dose is half cap, but consumers love them because they are even stronger when they use the 3 caps they are used to. (of course, they are using 6 times more softener)
And of course anyone would think that it makes the problem even worse for us. the answer is NO. Our washers still don't smell and we still don't have problems with mold.
As I said before, the only way to have nasty odors or mold in a front loader in Brazil is when people keep the door closed after use.
And at least on my washer (Electrolux Ecoturbo - Same Frigidaire Affinity in the U.S.), i never had to keep the door wide open. I close it until the door is out of the way, but without locking it. Theres a only gap so small that wouldnt fit my finger. but after years, it seems to be enough to make my washer smell like new after years of use. And I never keep the dispenser drawer open only because i'm too lazy to do that. I just remove it to clean the residues once a month and I never had mold in it too.
Other thing I also noticed: When I use brazilian detergents (Ariel, Omo, Ype, Ace,) or argentinian detergents (Skip, Ala, etc), no matter if they are powder or liquids, after a week without using the washer, i notice a very delicate SOFTENER scent in the washer, the last softener I used.
When I use american detergents (Tide, Cheer, Purex, etc) also both liquid or powders, after a week I notice a strong DETERGENT scent. Sometimes i can even run two or three loads with different detergents and softeners and the machine still smelling like the american detergent I used before.
When I use scent boosters like Purex Crystals, in a single load, the machine smells like it for several weeks, after more than 10 loads.
Also, when I run a load with american detergents, i notice the drum is still slippery after the machine is dry. and it doesn't sparkle as it should. It's hard to explain, it's some kind of oily film. And when I use any other detergents, the drum is dry like new right after I unload the machine and the drum sparkles like it was polished