Exactly, with your example, you've put in 15K, and after a year, you've lost £9,000, as opposed to a smaller deposit meaning you've lost £5,000. Depreciation.Sorry I still don't get why the upfront cost makes any difference?
If you decide to P/X earlier, the difference between what you owe and what the trade in is is just smaller if you put in a high upfront payment vs. if you put in a lower upfront payment.
E.g. if you want to P/X after just 12m in this example:
£5 deposit/12 monthlies of £453 = Total £10,436 - amount still owing about £30k
£15k deposit/12 monthlies of £146 = Total £16,752 - amount still owing about £24k
If they offer you £30k in P/X then you break even on the £5k deposit and end up spending about £10k.
If you paid £15k up front, then you are £6k in positive equity, so you've paid £16k and now have £6k back in equity and have paid....£10k.
Keeping the cash in the bank is one argument, but unless you have a way to invest it that returns you better than the interest you are being charged on the PCP (4.9%), then its not the most sensible thing. Some people like having the money there for a rainy day though. As I said, its a personal preference. Neither way is better.
That's your opinion. I disagree. I believe it is better to be as liquid as possible, for whatever scenario may happen. Ploughing all of ones money into a car which they likely can't afford (hence why they're choosing PCP in the first place) is an unwise move to make if you suddenly have to pay for something that isn't covered by the warranty for example, or if you find the car isn't up to expectations and you wish to change it.
Also don't forget, the GFV doesn't change if you put a higher deposit in. Yes you have a smaller amount to pay overall, but you are wrong in thinking that you are somehow going to be in positive equity down the line on a long term PCP. That is all down to market rates as I said before.