  Several functional renormalisation group (RG) equations including Polchinski
flows and Exact RG flows are compared from a conceptual point of view and in
given truncations. Similarities and differences are highlighted with special
emphasis on stability properties. The main observations are worked out at the
example of O(N) symmetric scalar field theories where the flows, universal
critical exponents and scaling potentials are compared within a derivative
expansion. To leading order, it is established that Polchinski flows and ERG
flows - despite their inequivalent derivative expansions - have identical
universal content, if the ERG flow is amended by an adequate optimisation. The
results are also evaluated in the light of stability and minimum sensitivity
considerations. Extensions to higher order and further implications are
emphasized.
