I too have a late 1970's 10 speed in the shed and last year bought a new hybrid. There was an Avanti (New Zealand made) bike sale and there were 3 bikes left. The women's bike was not my favourite colour, so I went for a men's bike. At the time we bought 2, one large and one medium (each $600 Aust).

I am 5'6" with 31" inside leg too and found the men's bike to be no problem. Just lift your leg up and over the back wheel (it helps to lay the bike over a little). The top bar of the hybrid women's bike was only about 4" lower than the men's anyway, so I thought it would not be that much different to mount.

Even though I ride the medium, I am just as comfortable on the large. (Have my seat the same height as HB's) Seat height was adjusted so I could touch the ground with toes bent (both feet) while seated, but now after a year, I have adjusted it so I can only just touch if I lean to one side a little. This height seems to suit my leg length, I still have my knee slightly bent on the down stroke and it feels comfortable when I ride.

I find the hybrid good for sealed roads (though I have not experienced the feel of a modern road bike to compare) and also ride quite a bit on unsealed roads and tracks without experiencing problems. I like the wider profile tyres - a bit extra grip in the rough. The 10 speed tyres are narrower and I don't feel as confident on unsealed surfaces, so avoid those when on it.