time to buy a wetsuit

They are both good suits.  I've been using an Orca Alpha for about five years and love it.  Anyway you can get in somewhere and try a few different suits on?  I have found that the cut can vary from one brand to the next and some just feel better than others.

You should not have any gaps in the neck that would allow water to enter.

This is not exactly true.  A wet suit is designed to let in a thin layer of water. That provides an insulating layer between you and the colder water.  However, you would not want a suit with a neck that let in so much water that it rushes through, or pools inside the suit, because that wouldn't ever be warmed by your body.

I know you already bought a suit, but I wanted to let you know this so you weren't worried about tightening the neck too much when you wear it.    That would quickly make swimming in a panic.   

is there any data on fastest wetsuits?

Great. Here's my wisdom:   If you put it on the first time and it feels like it fits

... it's too big.

And how you install the suit on your body will make more of a difference in how it performs in the water, than the difference from suit to suit.  

good luck, and have fun!