Are you a MoCist or a collector? If you’re a collector, get the two Matoran. If you are a MoCist, then you’re on your own. It depends on what you want more for building.
I’m a bit of both, alot of my 06-10 BIONICLE sets have been scrapped for MOCing (along with my CCBS sets, and Technic sets), and my 01-05 sets have been kept in tact.
How many Rahkshi do you have? How many '03 Matoran do you have? Get whichever one will most complete your collections.
(Eg. Get Panrahk is you have more rahkshi, get Hewkii if you have more '03 matoran)
This is how I justify all my eBay purchases. Then I buy lots and complete whatever collections are started from those and it’s just a never-ending cycle of collecting and buying lots.
If I were to get either of the aforementioned two it would be my first Rahkshi (though I do have the stars Rahkshi), and ifI got Hewkii he would be my first 03’ Matoran. I don’t have any 03’ sets and I though both of them looked cool when I was searching online.
Hmmm… Then go for Hewkii. He’s got more story importance (If that sort of thing matters) and I assume you have another version of Hewkii, either Inika or Mahri. If not, then still Hewkii.