The second one should be faster, as you get rid of sqrt(which is very CPU costly) and still have the core. The only thing you need to do is to ^2 everything compared to it, else things will go wrong. You probably knew that already 
Kudos! Heard about sqrt before, yet wasn't so sure about it (as this operation is not that widely used with accounting)
What are you making btw? 
Well, seeing what community have achieved so far (love your minimap ang leaderboard gadgets in particular) plus imagining what can still be done, multiple ideas are swirling in my head...
First things to try are:
- a semi-random (or fractal maybe) generated map, as I'm highly impressed at EverSwarm's replayability rate.
- Own rally system integrated in it, as same EverSwarm gets me tired because of all seed sendings at Endspiel.
- An occasionally discovered nebula-like visual effect may also happen to be included, if I'll manage to make it look fine all the time and not just sometimes (consists of a bunch of huge, highly transparent, partially overlapping DrawSprite's with different colours - ID 1 and/or 5, and, sometimes, slow backdrop colour changes).
Next steps then would be to make a preview thingy for abovementioned map generator (ideally, with ability to change parameters used to generate it) and somewhat that could humbly be named as AI...
Most part of necessary knowledge has already been collected. Though it may happen so that I won't get much time daily to progress there, so it could be way too long before I release something.
Also, if anything that is to come from me has to be finished, it should be pretty much optimised. Currently using P4 2.8 (single core) / 1 gb ram / radeon x1600 pro(512). Default Eufloria runs just fine, but any lag coming from unefficient code is spotted easily and painfully

Knowledge about new PC Eufloria version that is to come doesn't bother much. I'm pretty sure that men who gave birth to the game will want at least to enable support to the levels that previously included Community Map Pack consists of. Maybe not right at release date, so what?