If you're going to do the hike up Acatenango, do yourself a favor and book the doubleheader. The hike up Acatenango is pretty difficult, so once you get up there you might as well make the most of it instead of rushing right back down the next day! We had a great time with Old Town on the Doubleheader. Everything was perfect from start to finish, including transfer to and from the airport. Carlos was our guide on the doubleheader, and he was super friendly, knowledgable and encouraging! He also made delicious food!!
We lucked out and were the only two people on our tour, and I highly recommend it. Our campsite was right across the valley from Feugo, so we could see the eruptions at night while staying toasty in our tent. We brought our own equipment (sleeping bags, mats, etc) except for the tent, and the tent they gave us was a very roomy 3 person tent so we were super comfortable.
The main difference between the 3 day/2 night hike and the 2 day/1 night (other than obviously being longer) is that you don't have to get up at 4am to summit Acatenango on Day 2, you have the choice to sleep in and do the hike mid-morning to avoid the crowds. You also have the option to hike Feugo at sunset. This was the most incredible part of the trip, as you get pretty close to the eruptions and the sunset is gorgeous. Make sure you bring warm clothes and gloves, as it gets cold once the sun sets! We hiked back in the dark, which was great because it wasn't hot at all and it felt like it went by so quickly. We also got to see Pacaya erupting at the same time (which hadn't happened for months at that point) as Feugo on the hike back, which was pretty awesome. You definitely get what you pay for on these tours, so I would highly recommend spending a little extra and going with Old Town! They know what they're doing and had the best base camp site!!