The NHS in Wales spends more on health than England but has lower levels of productivity and poor performance on waiting times, a policy group found.
The Nuffield Trust compared the four health services in the UK, and found England spent the less but made better use of its resources.
Wales came off worse in the report's many comparisons including hospital doctor and nurse productivity.
The Welsh NHS Confederation said the findings painted a misleading picture.
The report, which looks at health statistics from 1996/7, 2002/3 and 2006/7, highlighted some of the differences in health policy between the four countries, including the introduction of free prescriptions in Wales.
It said the four services had had massive increases in funding - or "feast" years - following devolution in 1999.
But it warned the feast was likely to be followed by a period of famine.
It said: "The government in England used the years of 'feast' to reduce long waiting times, and governments in other countries may find it hard to catch up with performance in England during the years of 'famine'."
Wales, like Northern Ireland and Scotland, had had high rates of expenditure and hospital staff but lower levels of crude productivity and poorer performance on waiting times than England.
The report found that by 2006:
• Virtually no patients in England waited more than three months for an outpatient appointment, whereas 44% of Welsh patients did;
• Nearly all English patients were seen within six months for inpatient treatment by 2006, while in Wales 79% waited longer;
• Wales had the highest rate of GPs and outpatient appointments;
• Wales had the lowest rate of hospital day cases.
Mike Ponton, director of the Welsh NHS Confederation, said the method used to measure performance was severely flawed.
"The report measures performance in terms of productivity, but this method misses out much of what the NHS does and fails to measure what really matters - the quality and safety of care.
"High levels of activity, such as in-patient admissions or outpatient attendances, are not necessarily a good thing.
"What really matters is keeping people healthy and out of hospital - what we want to see is reduced hospital attendances and admissions.
"More sophisticated methods are needed to measure the quality of care, whether the patient is made to feel better, and whether they are satisfied with their treatment - not how many times they have turned up at the hospital doors."
He added a lot of money had been invested in public health in Wales, which would "reap rewards in the future".
Merthyr GP Dr Jonathan Richards said he was pleased to be working in the Welsh NHS rather than the English one.
"I think it would be like comparing two different types of fruit and if they are expecting a banana and they are fed an apple, they're going to say 'why aren't I getting a banana?'.
"The Welsh NHS is a lovely apple and there are lots of good things about it."
A Welsh Assembly Government spokesman said the report had acknowledged the NHS in Wales had made steps to improve services and care.
However he added: "Despite this overall acknowledgement of our progress, much of the report is dated, and therefore does not accurately reflect the NHS in Wales today.
"We have a legacy of ill-health and more people with chronic conditions due to our industrial heritage. We have therefore had a twin track approach of focusing on improving health and driving down waiting times for treatment."
Conservative assembly health spokesman Andrew RT Davies said: "Patients and staff have long had concerns that too much money is wasted on bureaucracy and not enough is reaching the frontline, where it could make a significant difference to the experiences of patients."