Here are a few observations about the different masks I've tried over the months. I wasn't very invested in researching this before I was vaccinated because I was a hardcore hermit. Now I ride the metro and go into stores if wearing a mask.

My favorite mask so far

The 3M 9320 (UK/EU), 9205+ or 9210+ (US) is comfortable, has a good seal, doesn't fog glasses, and (probably depending wildly on market conditions) is possible to get for a decent price.

I've only tried the 9320 which is the same as 9205. It has rubber bands. The 9210 has fabric elastic bands which people say are more comfortable, but also tighter, so might not be good for larger heads.

Other masks (UK)

• 3M 8810 unvalved FFP2: good seal, pretty comfortable, does not fog glasses, does not physically interact well with glasses. simple design, guessing it's a workhorse in construction. the straps are simple rubber bands, strong and effective but can catch in hair. it has a foam strip on the nose to improve seal, which seems to work well. the rest of the edge has nothing special on it. but it's pretty comfortable and seems to seal well.
• PurifyLabs FFP2 from Lloyds - bad seal, more comfortable on face than 3M, less comfortable on ears. fabric ear straps.
• QQQ PPE valved FFP3 from Lloyds - good seal, pretty comfortable, don't know about glasses yet. Elaborate design with nicer materials, has a special sealing material all along the edge, nice fabric bands. but it doesn't have special foam in the nose area, and this is where leaks happen most. from my brief tests in my house, the seal does seem to be good, but my amateur assessment is that special material to fill the nose gap is a good idea.