if you need a handwriting app, what features do you like?

As you see there are many handwriting apps in the market. which one is better to use?

Why i'm gray? Others are green?

The single best handwriting app is Graffiti (tryi) now owned by the Access Co. Ltd. It's good enough to run without any support, which is good news for Access Co. who seem not to give any, anyway. ;-)

It takes some getting used to - they all do, of course - but it is as fast as using a keyboard and far less fiddly to do so than using a tiny phone keyboard. Help is available every time you write your stroke outside the input box. Can't be modified for unusual characters, e.g. with accents, but that's a small price to pay for the otherwise ideal input method.

Excellent! Try it (for a few days, at least).

is it supports PDF expert? is it allows you to sketch symbols, numbers, pictures, mathematical equations?

It writes letters, numbers and symbols as a keyboard will do, in 'Roman' (like this) or in Japanese. It's quite different to your app 'Handrite'.

I see. I will go to have a try. you can try the handrite also. Maybe you will like it.

I think the most important feature should be "fast recognition", it should be smart enough to guess what you are writing even before you finish

If you need “recognize”, you have to “train” the app to read your writing as well as the interpretation errors that still occur. So the Handrite does not try to “recognize” your writing. Instead, it simply captures your strokes exactly as you drew them. It also means that you can sketch symbols, numbers, pictures, mathematical equations, etc.
Don't you think it will better?