The engines, chassis and drive train of most diesel pushers are reliable. I don't see many complaints about that part of the RV.
Since you already own an Itasca - you know about how well built (or poorly built) the Itasca coach is built. I would expect you will have similar quality and issues out of the DP version as you do your current rig.
Assuming you are looking at buying from the same dealer - the post sale and warranty service should be about the same.
You are on a Ford F53 chassis now with a 248" wheelbase and an operating weight in the low to mid 20K range.
To get a similar rear bath floor plan in the Meridian you have to go to the 42E - which is a 44 foot long coach - with a tag axle and a 279" wheelbase. It weighs at least 30,000 lbs, probably closer to 34K.
That's a lot bigger rig.
The 36M is closer to your current rig in size and weight - though a few thousand pounds heavier.