This has been a long debate. When I was in your position, I did alot of research. In the end I deceided to purchase a Jetprop for the basic reasons: 
Jetprops are: 
1. less expensive to fly 
2. less expensive to maintain. 
3. better engineering, thus better performance. 
All I can say, If the Jetprop fits your mission it is a great plane. I looked back and Mac Lewis a Jetprop owner did a great analysis. Here it is; 

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mlewis wrote:Dan; I have had this conversation with several folk, and would be happy to discuss it with you. I love my JetProp, and consider it a great value, performs well, is cost effective, great for longer trips (I tend to fly 600 - 900 nm legs) and fun to fly. I think I am able to discuss this even handedly - one of those I have talked with even decided to get a Meridian! 

Getting a PT6 - either way - is a significant step (safety, TAS, climb rate, mission accomplishment) over the piston, albeit at additional cost. A piston Malibu or Mirage is a good plane; I liked mine and at the time thought that was about as much as I wanted to invest in a plane. Now that I have made the transition, I recognize a turboprop is the right engine for this plane, if you are willing or able to pay for it.

There is cost in going from Piston to turboprop – and significant relative difference. By contrast, there is less difference between JetProp & Meridian. In picking between JetProp and Meridian, there are a variety of factors to consider; some of which depend on your intended use ...

1.) Price: If Meridian is being considered at or near retail price ($1.5 mil +/-), then I don't think the extra cost over a JetProp is justified. Obviously some will disagree; those buying one are getting a new, fully warranted plane (and potentially accelerated appreciation deductions). Some would argue that even at the same price, a JetProp is better decision. – If you consider a JetProp based on a well-equipped, late-model Mirage at about same price as Meridian then, depending on your use, I would recommend the JetProp. If the Meridian is not upgraded with Piper’s latest gross weight increase, then – by comparison – I would suggest you be willing to pay even more for a JetProp; especially if your typical trip is longish (over 700 nm?).

2.) "Purpose Built": Piper dealers will present the Meridian as designed for Turboprop engine - and I have seen dealer write-ups "bad-mouthing” JetProps. Some of what I have seen written is wrong and perhaps disingenuous. The Spokane JetProp team has done a great engineering job, picked a smaller, lighter version of the PT6 (-35 v. –42), giving good performance characteristics at low operating cost. The JetProp is safe, well tested & engineered and a good choice; don’t let the Piper dealer network scare you. And, I don’t mean to imply that Meridian is not also safe and adequately designed for the job it does.

3.) “New plane” v. older. You can get a JetProp based on a new model or older model Malibu/Mirage. These are available at different costs, airframes with different total time, avionics and appearances – but offer similar flying capabilities. A Malibu or earlier model Mirage converted to a JetProp will generally have better useful load than a later model Mirage converted to JetProp. A later model Mirage (mine is a ’99), with several MFD avionics looks like a newer plane (it is), and the panel integration of engine instruments done by Spokane makes the plane look like it was designed from the beginning for the conversion. A Meridian is a newer plane (2001, or newer). My point is that when considering a JetProp v. Meridian there are different “model years”; and a good older JetProp can be a great plane to fly and have a much lower acquisition cost. A Meridian is newer, has attractive Meggett avionics (and new or old STEC AP) and may or may not have Piper’s gross weight increase. Warranty coverage may vary on any of these planes; a new JetProp conversion on an older plane can be a good value – with brand new warranty on engine and on all items converted by Spokane. In considering “JetProp v. Meridian” there are several variables – at different price points. Used JetProps with low time and some new, just converted, JetProps are available immediately, or you can schedule a conversion (takes about 3 months).

4.) Weaknesses: I’d like to see an article about JetProp v. Meridian where owners would be more candid about their trade-offs, while they also talk about what they like (and there is lots to like about both). Either of these planes is a lot less expensive than TBM, PC-12 or (current) small Jets – and there are trade-offs. If either of these planes can do your job they are great values. Gross weight is a limitation on both JetProps & Meridian. If you need a lot of useful load, at full fuel, you almost need a Pilatus – for lots more money. This gross weight is a certification limitation; either plane will climb faster and use less runway at gross weight than a comparable Malibu or Mirage. JetProp has an IAS limit of 172; this leads to lower actual TAS at lower altitude. At cruse altitude, I routinely achieve TAS of 260+ (summer or winter). Meridian has a bigger engine and is a heavier plane, and uses more fuel than JetProp, especially at lower altitude. Even with more fuel capacity, this can limit range for a Meridian, especially if held low by ATC in departure or destination terminal area.

5.) Resale Value: Which plane will hold it’s value better? I don’t know. For Meridians, “hold value” compared to today’s Meridian “market price” of about $1.1 mil, or compared to Meridian list price? Meridian has the advantage of being the “branded” model from Piper, and there will probably be more of them in operation than JetProps – more visibility, “brand recognition” and sponsorship from Piper dealer network – so, maybe more demand from future transitioning pilots. On the other hand, JetProp has hit their target of being economical to operate (possibly as low cost per hour fully loaded, including maintenance, as Malibu/Mirage). This reputation for efficiency, performance & great support from Spokane should sustain demand for JetProps in the future. – And in most cases, acquisition cost for a JetProp is less.

6.) Training & Proficiency: These are faster planes. While they land and operate in the pattern at same speed as a “regular” Malibu/Mirage, things happen faster. I would suggest that if you are considering moving up to these (or any other) turboprop, that you be prepared to devote the time to remaining proficient – for your own safety.

Good luck with your decision.

Mac Lewis

I hope this helps. If you have any questions, feel free to call me my cell is 201-602-4512. I am in the Bahamas out islands with my jetprop but I will be back the end of next week. 
Fly safe. 
Mike Nestico