With two children a childminder is generally a little lower cost but not as convenient.
You need to list the pros and cons of each option and decide what is important to you.
A nanny just cares for your children - they are your employee so can be told what to do.
A childminder providers a care service to many families, they decide what they do and how they do it.
A nanny comes to your home, your children could still be in bed when your nanny arrives.
You take your children to a childminder, so you need to get yourself and your children ready in the morning and take to childminders.
You employ a nanny so have employer responsibilities but good news, there are companies that can help with the paperwork, such as www.nannypaye.co.uk who will help with payslips, contract, pension and remind you when to pay HMRC.
You use the service of a childminder for which they charge a fee. You pay their fee, you don't have admin to do or payments to HMRC.
Childcare funding schemes vary, both childminders and nannies can accept childcare vouchers or tax-free childcare (nannies need to be registered with the regulator to accept these schemes). Some childminders may offer 15/30 hour education funding.
Childminders and nannies will take/collect children from pre-school/school but do check which ones a childminder will collect from as they have other children who they also need to consider.