Chris, The rechargable ones are rumoured to be more watertight. (No issues battery compartment opening and shutting / resealing). Of course being rechargeable, no need to carry spare batteries.

On the downside not easy to recharge if you're away from home say camping. Whereas batteries are easily replaceable.

BTW Those bouys you / your club sold to us were in full use today - thanks it was a good deal.

indeed which one is which then? my mates dad used a green one to lay out the triangulation marks so were they too far apart if the green one reads slower?

  Got the foretrex 201 , very pleased with results, for v.m.g set waypoint downwind about 40 miles downwind, upwind give a - vmg speed . Iv set my display to show turn ie angle to downwind, v m g ,speed, set record to 3 seconds will last 3 races this gives good results on computer, no water under glass yet and at less than £140 is a must, good start function with syn 10 mins countdown then count up, good for all like walking but no map just track and backtrack ect. not class legal but fun for practice 15 hours between charge. iv got 4 garmin units and this is just as good as the rest.

   I looked at the Velocitek S10 but as the waypoint used for v m g is so close it would be hard to evaluate as it is only downdind if you are directly upwind of it?

so Waypoint 60 miles away you are allways upwind for vmg.

Only suppied with serial connection no ubs

im thinking if these gps units go on your wrist then is there actually anything in class rules (laser specifically but anything else also) to stop you using them. after all they are not attached to the boat are they? Or do class rules say competitors shall not carry a gps unit or whatever.