Dan I have just had a look on youtube, and searched for Discovery 5 engine issues, lots of the vids are not just engine issues, seems the list is endless.
You might want to do some research on the TD6 SDV6 3.0 engine and possible crankshaft issues.
As said above by @Firebobby1 defo do an mot check, you can see straight away if they have been scrimpng on tyres/brakes etc, and if that is the case...
I would go for the first one and join the Regret Club.
Second one seems boring and run in, more likely last longer than the first one.
Best option wait for better opinions who suffer from driving the vehicle to guage.
Besides welcome to landyzone...
If the first one was serviced at Land Rover dealerships you should be able to get service history based on VIN. Then you can see if it had recurring problems and also if it as regularly serviced.
A quandary...
should I buy (i) 2017 HSE Lux 55,000 miles with three previous owners from approved dealer - should I worry over the high previous ownership over 6-7 years? It's an ideal colour and configuration.
The alternative is an HSE 2017...