The main area where LED grow lights generally fall short of their HPS equivalents is in the coverage area. They deliver high PAR in the center, but it tapers off quickly, which is why they're generally less effective during flowering. Since you're growing in a fairly confined space, coverage...
HPS works fine, just not as well as MH. You could always supplement the HPS light with some cool fluorescent bulbs. They're cheap and they'll add some blue light to the mix.