In addition to frame size, you need to look at top-tube length because that determines how far you need to reach to the handlebars.

Looking at the specs for the Dolce 48, it has a seat tube length of 43cm centre to top whereas the Pilot 2.1 50 is 45cm.

Both bikes have very similar top tube lengths, 50.6cm (Dolce) vs 50cm (Pilot) this is about 1/4 inch difference so reach will feel pretty much the same on both bikes.

Given the above, it is just a question of which bike you prefer - you need to take them out and ride around a bit, the bike store should be happy to let you do that.

Hope this helps.