Oval crimped acrylic brushes generally differ from round ones by having a more user friendly shape.. The 'belly' of the brush is slightly squashed or crimped at the base, further enhancing the oval shape matching your nail plate shapes. Because of its shape, an oval acrylic brush won't absorb as much acrylic liquid, making for easier work, better beads and more control for intricate designs. It's often favoured for work with and used by 90% of nail techs being expert and beginner friendly.
On the other hand, a round brush typically has a bigger 'belly' which absorbs more acrylic liquid. This allows nail techs to pick up bigger beads for faster work and is typically used by more experienced long time salon nail professionals.