This is a bit off-topic, but decided to give you an answer.
eeehm, do not see any reason why a webmaster needs knowledge in HTML, Because they pay others or use scripts. But still it is always better to know at least the basics.
Ontopic:
I do agree, PDO is a build in solution so you can basically be sure that everything is safe, unless you are the one who screws up. Also it's future proof compared to mysqli. Both are fast however pdo has more adapters, So...
About it being easier, Well, Maybe like said above it is more about preference, However I got my own class for the database with pdo inside it but that could have being done easily with mysqli also.