I have both and still want both..for clones and young plants the MH makes them thrive
and you can use an enhanced red spectrum bulb, i.e. agrosun gold or sunmaster make one, about 65 bucks either way
the HPS is much warmer and can be used by itself with full spectrum bulb such as hortilux...which has enhanced blue spectrum close to 100 bucks

you can use the hortilux/blue all the way through grow and if you also have a MH with enhanced red spectrum you could probably use it throughout entire grow, but,
If you have both with enhanced bulbs,respectively...you cou start with: (or use both all the way thru)

enhanced MH for 2-3 weeks then add enhanced hps for warmer spectrum and increased lumens(like the middle of summer), then remove MH or turn it on only; during the middle of light cycle each day using the enhanced hps for finish, up to harvest,
the last 2-3 weeks...

Yeah I would say, if you can have both then have both...I love the MH on clones they just thrive under the white/blue spectrum...just my $.02