I also have both.
I have owned 3 P38's, 2 of which, including the current one, were ex police, all of which were used with some decent mileage on them. I have had to do most of the known P38 tasks on them, Jammed distribution flap, leaky coolant connections & EAS air bags, but by and large nothing that any true sadistic Land Rover addict would consider too much.
You all know what i mean
I added a 4.4 HSE L322 in about 2002/3, purchased brand new from a dealer and it's mainly the wife's drive so has never seen off road action and even today has no more than 30/35 K on it in very nice weather, well we are in Cyprus.
Within weeks, we had a loose bolt on the front sub frame giving a knock, failure of the head lamp leveling ECU which took a year to get a replacement, and we had the instrument pack replaced due to missing digits and door pads replaced due to handle sagging, fortunately under warranty as they are like 700 GBP each, As per JC the column motor packed in which is due to excessive tightness and required resetting several times until it was bedded in. Mind you the column eventually broke all together, requiring 600 GBP's worth off replacement, on which the motor quickly packed in altogether.
I had to replace a leaky pipe at the rear of the engine, apparently common, a corroded radiator, the condenser / heater matrix which was a very major dash out job, a lower screen scuttle plate, again a known problem which vibrated at speed, a duff fuel pump, again common, an air suspension compressor, as a formality upgrade, a 1300 GBP MID display due to lost digits, and as we speak it has been laid up for months due to having a leaky air bag. Of course i had the front diff and Prop changed as well. There are also other endless problems it has and things i have forgotten to mention
This ain't a pop at the L322 It really is a nice car, when i drive it, it always re amazes me how nice it feels, how precise pointed and capable it is. I love it, and technologically wise its light years ahead of the P38, I really do just wish i could drive it for more time than i spend fixing it.
To be honest at 30K the thing could probably use a service, and if it had ever given me some, i might be willing to throw in the bits for that, although i do vaguely recall having already tried that tact before in the hope of soliciting some degree of continued enjoyment and use out of it.
Now it sits in the corner of the garage and has done for several months with it's front left corner sunk to the floor constantly begging me to buy it a 600 GBP EAS airbag, and one for the other side as they should be changed in pairs. However that would be the same garage from which SWMBO takes the P38 to go get the shopping every week.
There is a lot to be said for the L322, but there is also an awful lot to be said for the P38.