Devils Advocate - so not shouty and being snooty.
Based on Sasquatch inside info and other info on the forum, at least 4 things to look at:
1) environmental,
2) legality
3) price
4) potential pros/cons
1) Environmental:
The engines are quite complicated compared to the 'old days' and without the mipmaps and the goujons installed, will give more NOx, particulates and possibly other nasties. However, the mipmaps and goujons do result in extra useage of diesel so reducing mpg slightly.
Also, however, the NOx and soot doesn't just 'disappear'. It gets burnt off, so producing other combusted gasses and products that governments are happier to turn a blind eye to (If you don't test for them, then there isn't a problem) rather than the demon CO2 and NOx and larger particulates. So - these aren't 'clean' engines with the DPF/adblue in the sense that there are still emissions. No such thing as zero emissions unless you have a hydrogen powered engine (if you discount water + heat) or an electric engine powered by renewables. We won't go into production/mining/transport/slavery in this post just yet.
2) Legality:
At the moment, although illegal to drive on roads with emissions devices that have been tampered with in any way, it is unlikely (not impossible) that you would be caught out for the next 3 or 4 years unless in a major accident or have a major insurance claim, or are rude to the wrong traffic officer (as in, one who knows what a DPF looks like) or that rare occurrence, a checkpoint looking for such anomalies (you'll know it when you see it and are just about to pulled into one).
3) Price:
The price of a new DPF is about £800 to £1200 ish. Expected to last over 5 years(?) depending on driving style. The price of a new Adblue system is about the same (expecting not to replace it within the lifetime of the vehicle but a few are unlucky in this respect).
The price of a remap and blank DPF is about (at a guess) £500 but would have to be put back to OEM in 4 years time at a cost of about £800 to £1200 (ish).
4) Potential pros/cons:
With a remap - in theory - not insured and illegal to drive on the road.
With a remap - get a bad one (not all are good looking at forum) and it'll cost you loads to put right
With a remap - get a good one and you are cruising.
With a remap - either mapped for extra va va voom OR for extra mpg - not both.
You pays your money and you takes your chance - but all this talk of taking a vehicle to someone who has just come out from having a holiday at his maj's pleasure and giving them money to fiddle about with your engine/cpu, that is too much for me to bear. I know that doesn't apply to many (more than 1) but at a guess, if a garage that is doing this gets it wrong, I can't see what comeback you have as you have asked for something illegal to be done in the first place.
Admittedly, before reading lots of stuff (mostly on this forum as I can't be arsed with most of the rest of the internet), as soon as I got my van I was doing research into getting rid of all the 'potential problems'. Less stuff on there to break, less stuff breaks. Now I look on the system as a bit of a needy friend. All good for most of the time but will eventually have to replace it - like brake pads.
Personally, If you want a cheap vehicle, then go get one - but, each to their own.