I take em most of the time, whatever 109 I am in.
The G10 can't turn for snot anyway, so adding the Gondolas doesn't hurt in that respect. I almost always take the 30mm and two gondolas, unless I know I'm only going to fight a Pony of another 109, then I'll go 20mm and no gondolas in the G10. G6 I almost never fly, every time I flew it I took a 30mm and gondolas.
G2 I rarely fly anymore, when I flew it I took gondolas most of the time, because the 7.92s take about 400 rounds to kill someone with.
F4 I almost always take gondolas, because the plane isnt fast anyway, so slowing it down some isnt going to hurt it

. It still turns plenty well with gondolas, I can hang with Nikis until it gets down to the deck, at that point the Nik outturns the F4 pretty handily.
As a note, the F4 can't turn with a Spitfire at all, I've heard people say it can outturn them under certain 'circumstances', but I've never seen that to be the case.