I have been to both places. For Machu Picchu a lens like the 16-17mm on a full frame is wide enough. Best is to go up twice. Once end of the day second time early next morning. In between its crowded with people and like a park.
For Iguassu, do you plan to go to both Argentina or Brazil? From Brazil side you might need a long lens to shoot the opposite side of the falls and a wide angle for the nearer ones. I recommend a 12mm and something like a 300mm. Be prepared for lots of water spray. And bring a rain jacket/poncho for yourself. Argentina side is much more extensive and you can go much nearer to the falls. A wide angle is sufficient and the views overlooking the brazil side isn't that great.
Only been to Macchu Picchu. A bright wide angle zoom should suffice. Longer telezooms useful if you climb Huayna Picchu and shoot back towards Macchu Picchu (1 hour climb to the top). MP gates only open at 7AM. Sun rises from behind one of the peaks. Needs a 5 to 10 minute walk to get the typical postcard viewpoint picture that is zealously guarded by some guides. Don't do those jumping photos because the guides get pissed off if they see that and will yell at you with a megaphone.
Will get very crowded quickly, more so in the late morning and afternoon so go early or go evening. Get into the bus queue from Aguas Calientes at 5am. Best if you're staying at the $$$$ resort at MP then it's just a short stroll to MP. If you're hiking there from the Sacred Valley, check with your guide what time you arrive at MP.
I thank you for taking the time and trouble to share your experience. We are travelling with Trafalgar Tours and will spend a night at MP and will try to early morning or evening as suggested. Did you bring along a tripod with you ? Are the guides rather tourist unfriendly ?
already done your trip?
If you are going on free and easy, suggest bring light gears.
Some country are not quite safe. But touristy spot of Brazil are full with police.
MP is a place where I experienced extreme weather - cold morning and drizzling, up to MP then blessed with sunny day, but when back down to the town (Aguas Calientes) it rains again. That was Oct.
So be prepared - drink more water.
Yes start q for bus at 5 am. The Q was about 50 people in front of me. But I manage to catch the first batch of bus go up (about 4-5 medium size bus, 30 seater if not wrong) there)
MP opens at 6 am. Good to go in early.
It is allowed (not check) to bring tripod into MP.
I did not go up Wayna Picchu, only climb the cerro MP (MP mountain) up to half way (1 hour up).