I purchased my Pegas 30 from Denny and I can say I've never regretted it in any way. Have I cut anything that required the 30-inch throat... no, not yet. But it's there when I need it. I do plan on cutting large pieces in the future. I have the pattern right now for a piece that will be around 10-inches X 42-inches. This is a huge machine.
At the time I made the purchase, Pegas just came out with their 30-inch and Seyco just introduced their 24-inch. I was torn on which way to go. The Seyco had more distance between the blade and the front of the table, however, considering the Pegas blade clamps as well as the extra 6-inches, Pegas won the toss. The 21 would serve you well, I'm sure, but if you have the space I would recommend the larger, 30-inch saw.
Like I say, it is huge. My shop is unheated as well as having a few areas that drip when it rains. I purchased a 6' X 8' greenhouse popup tent where I house my saw, a table for my blades and a stool for a little 1500 watt heater that keeps me toasty warm even when the temp drops below freezing. I have a waste can for my scrap as I cut it out and a dust collector velcroed to the stand of the saw to catch the majority of the sawdust. (The dust collector is a styrofoam meat tray stuck to a piece of 1/4-inch ply cut to size and sits on the cross members of the saw stand.) Depending on how much I'm cutting, I roll up the door and give it a good vacuum when needed. The greenhouse has the large zip-up door as well as 2 zip-up windows that can be rolled up and secured. I don't think there will be an issue with it being too hot in the summer. If it is, I have several fans I can use to circulate the air.
Good luck on our decision. Regardless of which you choose, you won't regret going with a Pegas.