I don't think one can really answer, because what is good or bad for anyone's particular biology is largely variable. We can determine that, yes, generally, this kind of oil is pretty good or bad, comparatively, but when faced with relatively healthy oils, you'd be hard-pressed to say "Oil A is 15% healthier than Oil B".
We know that monosaturated fats are some of the healthiest oils there are for human consumption.
Also vital and needed for good health are polyunsaturated fats, which include Omega 3 and Omega 6 fats.
Saturated fats are considered less healthy, but even that is being re-evaluated in light of things that were done to avoid saturated fats (use of trans fat subsitutes, for example).
And trans fats have been found, after much use, to be pretty much evil for the body. Oops.
What are fats? The real skinny on healthy fats and harmful fats
The other answer referenced a specific study where it seemed that sunflower oil was better for cardiac health results. Obviously, more results are needed before anyone outside of a marketing department can declare anything definitive.
What is interesting is that olive oil is higher in monosaturated fats, but also higher in saturated fats, with sunflower oil having more polyunsaturated fats. of, is there an ideal ration of one to the other? Depending on the opinion of which factor is most important (let alone how a composite evaluation is determined), the question of "better" seems to be unresolved, at this time.
{PDF} Oils Comparison Chart
What is still at issue is that we know that "bad fats" are to be avoided, and "good fats" are a better choice, but here we have have, open, the question of whether one good fat is more helpful than another, and the jury still seems to be out on that.
If monosaturated is better, than olive oil would be the choice. If the amount of saturated fat is more vital, then sunflower oil. If polyunsaturated fats, especially Omega Threes, from any source, help reduce cardiac risk, then sunflower oil. If vegetable sources for Omega Three fats don't work the same as fish-based oils, then that advantage is not present, and we just don't know yet. You can't find any recommendations out there that give specific advice of more than one "good" fat vs another.
The potentially helpful types of dietary fat are primarily unsaturated fats:
Monounsaturated fatty acids. This type of fat is found in a variety of foods and oils. Studies show that eating foods rich in monounsaturated fatty acids instead of saturated fats improves blood cholesterol levels, which can decrease your risk of heart disease and may also help decrease the risk of type 2 diabetes.
Polyunsaturated fatty acids. This type of fat is found mostly in plant-based foods and oils. Evidence shows that eating foods rich in polyunsaturated fatty acids instead of saturated fats improves blood cholesterol levels, which can decrease your risk of heart disease and may also help decrease the risk of type 2 diabetes.
Omega-3 fatty acids. One type of polyunsaturated fat is made up of mainly omega-3 fatty acids and may be especially beneficial for heart health. Omega-3, found in some types of fatty fish, appears to decrease the risk of coronary artery disease. There are plant sources of omega-3 fatty acids. However, it hasn't yet been determined whether replacements for fish oil — plant-based or krill — have the same health effects as omega-3 fatty acid from fish.
...... Avoid trans fat.
Limit saturated fat to less than 10 percent of calories a day.
Replace saturated fat with healthier monounsaturated and polyunsaturated fats.
Mayo Clinic - Dietary fats: Know which types to choose