I'm not an expert, but given the integer factorization of two numbers $a,b$:

$$a = p_{i_1}^{a_1}...p_{i_n}^{a_n}, \quad b = p_{j_1}^{b_1}...p_{j_m}^{b_m}$$

>What is the time and space compexity of checking if $a > b$ ?

Suppose that the factors and the exponents are given in binary and the whole input over alphabet $\{0,1,\wedge,;,*\}$ looks like:
$$p_{i_1}\wedge{a_1}*...*p_{i_n}\wedge{a_n};p_{j_1}\wedge{b_1}*...*p_{j_m}\wedge{b_m}$$

What algorithms can be used?