Good to hear you are feeling a little more confident. Definatley hang onto your cash until you are ready to upgrade. I learnt an overcapitalisation lesson pretty early! On your next bike they will generally swap out shimano for sram of a similar level for pretty much no or little cost.

I test rode an 48cm bike the other day and I also have short legs but it felt a little strange. Mostly because it was ultegra and I got to the traffic lights and couldn't workout how to change gears! I am not in love having such a small frame, I also do a bit of triathlon and she looks very odd hovering on the rack

I went the smaller frame as I like a bit of drop between the handle bars and saddle. On the 48cm it was already with no spacers so I couldn't get any lower. Sadly for this reason I may be destined for a lifetime of child size frames.