I am a health professional and deal with this sort of situation every day.
If a person has lost capacity and there is no LPA then decisions must be made in their best interests - which would always involve consulting you.
If you were the LPA for welfare you could make decisions as if you were your parent. But those decisions must be demonstrably in your parent's best interest.
As you can see, there is not a lot of difference between the 2 situations. The other thing I would suggest you consider is the emotional burden on yourself of being an attorney.
I have one for my mum because I feel I know about healthcare, how to navigate the system and pretty much what scenarios will come up and how she would react in them - for me having the LPA is reassuring.
However I have seen people with them who were utterly unprepared and now their parent was dying were in complete agonies over whether or not they were making the right decisions. For them they would have been better not having the LPA as they were fully consulted with but would have found it emotionally easier not being the decision-maker. On this basis when my husband and I did finance ones for each other, we didn't do welfare as I think I could easily do his but he would find it very hard to be mine.
In real life, most people don't have powers of attorney for welfare and the same decisions get made at the same speed with or without them, more or less. As an only child you are spared all the disagreeing siblings scenarios as well. I'd say it's a personal choice depending on what is going to make you feel the most secure about what happens to your parents.