A string inverter is cheaper today. A hybrid leaves the door open to a battery without ripping the system out. Here's the maths behind which to pick.
A string inverter costs £600–£900 fitted; a hybrid £1,200–£1,800. If you fit string today and add a battery later, you'll either swap the inverter (£900 plus a day's labour) or AC-couple a separate battery inverter (£700–£1,100). Hybrid wins on lifetime cost for any household likely to add storage in the next five years.