Align Cells With Identical Data

I need to compare 2 groups of information against each other. Both sheets have column a- with an alpha numeric value, and column b- with a numeric value that corresponds to the value in the same row in column a. both sheets are sorted by alphabetical order in column A, the issue is sheet 1 has values that sheet 2 doesn't in column a, and vise-versa. i want to align the values in column a which will result in some blank rows in both sheets. I need to compare the numeric values in column b of sheet 1 vs sheet 2. thanks for all help.

for example:
sheet 1:
a | b

a1234 34.01
a1235 15.59
a1237 23.40
a1239 14.56
a1243 6.87

sheet 2:
a | b
a1234 33.00
a1236 25.89
a1237 22.45
a1238 5.45
a1240 14.58

comparison
a1234 -1.01
a1235 - n/a
a1236 - n/a
a1237 - 0.95
a1238 - n/a
a1239 - n/a
a1240 - n/a
a1243 - n/a