  We compare the explicitly correlated Hylleraas and exponential basis sets in
the evaluations of ground state of Li and Be$^+$. Calculations with Hylleraas
functions are numerically stable and can be performed with the large number of
basis functions. Our results for ground state energies $-7.478 060 323 910
10(32)$, $-14.324 763 176 790 43(22)$ of Li and Be$^+$ correspondingly, are the
most accurate to date. When small basis set is considered, explicitly
correlated exponential functions are much more effective. With only 128
functions we obtained about $10^{-9}$ relative accuracy, but the severe
numerical instabilities make this basis costly in the evaluation.
