I will offer my opinion and qualify the WHY
I have had tall chimneys with pellet stoves and cleaning them is a real PITA
Sadly these vents need cleaning quite often and an insert requires you to pull the unit out and then go about the cleaning process.
We have 3 pellet stoves in our home, and all of them have direct vent setups.
I can shut the stove down, let it cool, and then within less than 30 minutes have the stove completely cleaned, the leaf sucker run on the vent for a few moments to clear the ash buildup and good to go.
After having messed with the tall chimneys and such, the direct vent is wonderful.
Most new stoves run fine with this type of venting.
We have a Quadrafire 1000 and two whitfields running this way, and I would never look back.
The one Whit has about a 4 foot vent and the other Whit is less than 2 feet
We use our pellet stoves as our only heat source, since the house was built with 100% electric, which is ridiculously expensive.
This situation requires that we are on top of maintenance big time.
Many times during nasty weather, the stoves get what I call a "hot swap"
This is a "Shut the fire off " wait till the pot has no glowing coals, then clean it.
I use gloves to handle the hot parts and gitterdone.
At times I can get the stove back up in 15 minutes or less.
I don't even remove the ash baffles, just open the mechanical cabinet, unhook the vacuum switch hose to protect the switch, then use the leaf blower and suck everything.
Our stoves are situated such that they are fully accessible with the pipe connected.
This makes even a close encounter of the WORST kind easy to deal with. (Read this as any repairs that require digging into the inner workings and crawling around the unit)
Just some thoughts
Snowy