If you would pass a class 2 medical then yes it would make sense to have a class 2 if you thought you wanted to 'upgrade' to a PPL in the near future. And a class 2 would also give you validity for a LAPL. So you wouldn't have to pay again if you had a class 2 medical. Just any 'upgrade' fee from LAPL to PPL for the CAA.
Under 40 both last for 5 years validity. Over 40 the class 2 is valid 40-49 for 24 months and 50+ 12 months. The LAPL medical is valid for 24 months over 40.
But if money is short and you are very fit then a LAPL may be more cost efficient depending on what your GP would charge you!