I think it should stay at 16 but not result in automatic criminalisation of those under 16 who engage in sex. There needs to be consideration of the context and the emotional and social maturity of those involved. Perhaps that could also be the case for those just over 16 who have sex with those under 16 (i.e. they could only be a few months in age apart,) but that also would have to be weighed up on the context.
It's important to recognise the rights of the young person as well as the need to safeguard their well being when they may not be in a position to give full, informed consent for sex (and where they might believe that they actually CAN do that.)
I think lowering the age to 14 as a general rule would not be wise. As others have said, this would legitimise sexual contact between much older people and young people, many of whom are not physically mature, nor close to being emotionally or socially mature enough to fully understand the consequences of sexual relationships. Another worry is that if the age of consent drops by 2 years, that also indirectly sends the message that the "grey area" where sex isn't legal, but isn't "that bad" which we have in our culture will also drop. Now, it's notionally about 14, maybe 13. It could become 11 or 12.
What bugs me about these debates is when someone brings up the issue of physical development. Yes, girls and boys are developing secondary sexual characteristics at a younger age than they did say 100 years ago. But, just because a girl starts periods at age 9 doesn't mean she has the emotional or social maturity or the ability to understand the complexities of sexual relationships and possible consequences of this that an adult person would. Even very young children have some version of sexual feelings, have a awareness of themselves as sexual beings, but that's not the same as being capable of giving consent to have sex, particularly with an adult who has the capacity to manipulate and control the situation, thereby exploiting the child or young person for their own purposes.
Another thing that worries me about some of these discussions is the number of adults who insist that their experiences of under age sex, including sex with much older people, was a "good" thing. I don't doubt that there are some for whom this was genuinely the case. However, evidence shows there are a great many more who have been seriously harmed by childhood sexual abuse (for that is what it is,) and it has blighted the remainder of their lives. I also sense there are some who "cope" with having been sexually abused by convincing themselves that it wasn't that bad, that they were active and willing participants in sex, because this means they don't have to see themselves as victims, as controlled, as exploited. I sometimes wonder if this kind of thinking may be behind the words of some adults who maintain that having sex when a child "did them no harm." 