(N/A) Points of similarities:
$1$. Both show a common oxidation state of $+3$.
$2$. Both show a contraction in ionic size in the tripositive state along the series.
$3$. Both exhibit paramagnetism.
$4$. Both are electropositive and highly reactive.
$5$. Both form coloured ions.
Points of dissimilarities:
$1$. The dissimilarities arise because of: $(i)$ Lower binding energy of $5f$ electrons compared to $4f$ electrons. $(ii)$ Poorer shielding effect of $5f$ electrons compared to $4f$ electrons.
$2$. Actinoids show a large number of oxidation states (up to $+7$),while lanthanoids show a maximum oxidation state of $+4$.
$3$. All actinoids are radioactive,whereas among lanthanoids,only promethium $(Pm)$ is radioactive.
$4$. Outer electrons in actinoids are more easily available for bonding.
$5$. Actinoids form oxo-anions (e.g.,$UO_{2}^{2+}$),while lanthanoids do not form oxo-anions.
$6$. Actinoids react with non-metals at moderate temperatures,whereas lanthanoids require high temperatures.