multiple call to system task vs single call and call back

[kk]

I have in two clks in my verilog code.
clk1 period = 20 ns
clk2 period = 1000 ns
Now if i want get a signal value using pli routines during every event
on clk1, i can do that by
1. writing a system task which is called on in every event on clk1
2. writing a system task which is called only on event in clk2 and
registering a call back when there is a event on clk1.

which on is better and why??
thanks in advance.