The issue comes down to how the money is distributed and spent. The current Scottish Government has control over something on the order of 75% of the money spent in Scotland (the other 25% coming from central government in Westminister on reserved matters like defence). Conversely, as it currently stands (ignoring the new rules from 2016), the Scottish Government only has control over something like 15% of tax raising powers (again, everything else coming from Westminster).
Thus, if you were a party who wanted to promise cutting taxes to the population you could, but you'd have very little impact on the taxation's bottom line. I actually don't know what the Barnett formula says about money the Scottish government doesn't spend from Westminster (wondering if you could in theory as a party in Holyrood decide just not to spend the money you were given, as a forcing tactic).
Regardless, all parties (in both London and Edinburgh) and the Scottish population are in agreement, the situation of controlling spending but not tax raising is an unfit state for a government to be in.
Thus, if you were a party who wanted to promise cutting taxes to the population you could, but you'd have very little impact on the taxation's bottom line. I actually don't know what the Barnett formula says about money the Scottish government doesn't spend from Westminster (wondering if you could in theory as a party in Holyrood decide just not to spend the money you were given, as a forcing tactic).
Regardless, all parties (in both London and Edinburgh) and the Scottish population are in agreement, the situation of controlling spending but not tax raising is an unfit state for a government to be in.
[edit - make my 'all parties' comment clearer]