I'm going to use English descriptors for the pieces rather than embroil myself in the debate over exact names for each piece. Let's not obfuscate the issue!
Each style has an underdress, consisting of a fitted bodice with a pleated skirt and sleeves.
Each style has an overdress, but there are serious differences. You can get away without one.
Each comes with a chemise (ok fine, camicia) again with differences but easier to ignore.
Bodice: You're looking at a high, Empire-line bodice that cuts right under the bust. Look for diagonal lacings at the back laddering up the shoulder blades. The straps of some extreme examples barely stay on the shoulders.
Skirt: Pleated to a waist band sewn to the bodice. NOT OPEN down the front (that's the overdress).
Sleeves: Tight, finestrella (cut-outs), often in two pieces, tied to the bodice and each other. I have a lovely pattern developed from Albrecht Durer's sketch of a Venetian lady.
Material: Brocaded silk or velvet is favourite. The last 2 years Fabricland has been carrying some very believable light synthetic brocades that wash well.
Very similiar to the underdress, but with a front lacing instead. Long hanging sleeves are an option (I have an illumination of the Freschi family that shows this).
Skirt: Pleated as inthe underdress, but this one IS open down the front.
Material: same family as underdress, but often richer/heavier with larger motifs
Broad round neckline (to match dress necklines) with the fabric gathered in numerous pin tucks
Wide sleeves, NOT gathered at the wrist, longer than the wrist
Material: Very fine linen (or perhaps cotton)
Bodice: Tight, front-laced, closer to natural waist (the examples vary).
Skirt: Pleated as for Venetian. NOT OPEN down the front.
Sleeves: Headed, tight, often contrasting, vibrant brocade fabric to the bodice/skirt. Often tied to the bodice. One nice detail is a split about 4" long from the wrist, secured with a button midway. This is to allow the tight sleeve to be put on at all.
This is the big difference. Similarites to a male surcoat or cloak structure - 2 pie shapes to the floor narrowing to the shoulders (producing natural pleats), open down the sides from the shoulder. Mistress Eleanor Fairchild said she sometimes belts the front but not the back, to control the pleats while giving an attractive flow behind. No sleeves, of course.
Fabric: Lavish brocade, large pattern.
I have not studied this as much but if I understood her Mistress Eleanor Fairchild believes the sleeves to be very long and relatively form-fitting, to allow for the foaming wrinkles at shoulder, elbow (if applicable) and cuff. From my own review the sleeves are tight to the wrist.
Aelgyfa commented that Florentine women seem to wear more pinks and blues as opposed to the bright jewel reds, greens and golds seen in several Venetian paintings. On reflection I would disagree. Ghirlandaio (my Florentine drug of choice) does portray some rather sweet fabrics (a certain pink and gold brocade comes to mind), but the rest of his useful examples are not that dissimilar to the Venetian palette. Consider the many dark rich sleeve treatments in the profile portraiture.
Gozzoli's Procession of the Magi is another example to consider for Florentine colours (and men's headgear). Bear in mind that both cities had sumptuary laws that heavily restricted male dress colours, and governed the richness of women's dress. Paintings of the period often seem to have little in common with these laws, so be warned - just because you've matched a painting down to the last thread and pearl strand doesn't mean you could have flaunted your ensemble before the Medici.
I'm not even going to get into shoes (Venetian chopine styles vs. Florentine ???).