The current threshold for VAT is £70,000.
Advantages: reclaims are possible for the setup periods and low trading periods at the beginning which will allow you some positive cashflow.
Disadvantages: the minute your vatable sales exceed your vatable purchases you are paying money to HMRC.
Have you forecasted any works costs, purchase costs, sales revenue, overheads etc for the next 12 months? If so, an analysis of this will reveal which scenario would be better.
Generally speaking though, it would only be beneficial if you were spending a whopping amount on assets, refurb and other set up costs initially. i.e. The 1st quarter rebate covers the next 5 quarters payments - which tends not to be the case in food / beverage retail outlets.
If you have any further questions, please do not hesitate to contact me.