I also have 55g with open top, I debated heavily about which way to go.
With a closed top you have less evaporation and you may retain more co2, however for me there was no way I was going to keep up with the cleaning of the glass.
If you don't routinely clean your lids your PAR is quickly reduced.
Additionally, I run a 20lb pressurized co2 so I kinda got paranoid about fish gassing but I am seriously blasting co2 into this tank right now, so it probably doesn't matter that much
No lids = better gas exchange and no indefinite "lid maintenance"