Round headlights have a more efficient light pattern than rectangular ones, and are cheaper. Halogens of both kinds pull more amperage, and 100% of the current goes thru the headlight dimmer switch integrated into the stalk on the steering column. Extra current shortens the life of this switch which is almost impossible to replace if it fails. Adding relays to the headlights is a really good idea regardless of whether you change bulbs. The conversion kits for 'square' headlights are either expensive if you pay to have it done, or very difficult if you buy a kit. Not all kits are the same- one simply cuts the steel buckets in two and epoxys the pieces together at a diffrent position. If the glueing isn't done perfectly, the tops have been known to fly off, scratching & denting the roof on theur way.
