Several styles of fleece or jumper are available depending on your tastes:
Curved shape: ideal if you want something a little more aesthetic, if you like to wear your clothes close to the body or if your 3rd layer (coat or other) is already quite thick.
Loose fit for a relaxed silhouette: ideal if you don't like tight fits, if you have an "A" or "H" shape, if your first layer (your first garment against the skin) is quite thick, or if you just like to have your top below your hip drop.
On the aesthetic side of things, the finish is what will guide your choice.
Do you like hoods? Do you prefer a full zip to wear your fleece as an open jacket or a half zip to wear it as a jumper? Do you need pockets to put your keys or even your mobile phone in? Do you like colours or basic all-purpose items? Are you a little cold, but not that cold? Perhaps a gilet (which keeps most of your vital organs warm, without restricting the freedom of movement of your arms) would be more appropriate, especially in the mid-season?
In short, choose the finishes and models of fleece clothing that suit your lifestyle and style.