I use the strap. Nothing will ruin your day like dropping the box to break the TX... and having to just watch the plane do whatever it wants (because there's no TX controlling it any more.)

I have a sequence I follow EVERY engine start:

Aquire frequency control (pin or whatever method is used at the field)
Get the "tailholder" (Hey buddy... hold the tail please)
Lay out the tX, starter and glow adapter in an arc in front of the aircraft (all in easy reach)
turn on TX and aircraft
Check that all controls function and are working the correct directions EVERY time.
Set throttle to proper position for engine start. (high idle most times. Annoying engines need higher throttle.)
Prime engine (if it tends to need it...)
Connect glow
Start engine
Run up some to clear and reset to proper idle.
CAREFULLY remove glow plug and toss to the side.
Carefully move the starter out of the way.
Pick up the TX
Stand up and put the tx neckstrap on.
Run up the engine again.
When ready, tell the helper that he can let go so I can taxi out. (or have him carry it out or hand launch, if more appropriate to the situation...)
Go Fly.

Note that the neckstrap stayed attached to the TX... not on my neck to get in the prop durring starting.