I can't speak for the Jag engine in the LR, but the one (5.0L) in my wife's XJ has been worry-free and great. Not a single problem with only 125,000 miles so far.
A few (and too few) forum members will swear by the brief BMW foray into LR custodianship.
But in my experience, the 4.4L in my RR is the neediest engine I've ever had.
Between periodic oil leaks (more often than any other vehicle I've ever had), complicated PCV system that fails periodically, timing chain finickularities, heated thermostat failures, cooling system ruptures and transmission tantrums... just to name a few... I have considered ditching my 2003 (with almost 190k miles) giving a 2013+ MY a try.
Then there are the myriad problems all over that generation beyond the engine.
I know that things fail after 15 years & 189k miles, and if they were proportionately after or towards the tail of those years/mileage, I'd be more understanding. But it's way more needy than any of my other vehicles, a couple with more years and equal miles.
So it may be a great engine with proper care, if proper care includes relatively major maintenance each year of hundreds of DIY $$, or thousands of service shop $$.
"it is what it is". I hate that saying, but it feels like it fits the 2003 - 2005 RR.:doh:
Of course mine may be the exception rather than the rule. But if that's the case, there are a whole lot more 2003 - 2005 RRs on the road than I'm seeing.