Spring tides are about the same height whether at New or Full Moon, because the tidal bulge occurs on both sides of the Earth...the side toward the Moon ( or sun) and the side away from the Moon (or Sun). They will not be equally high because the distance between the Earth and Sun, and the Earth and Moon both vary and so will their tide producing effectiveness. The highest Spring tides occur when the Moon is at its closest to the Earth...the so-called Perigee Tide.
I hope this is helpful, I am not an expert on these matters and am relying on some general knowledge I have acquired over the years that I think is mostly correct so far as it goes. Tides are a big deal for shippers and oceanographers so I would bet there are many fine books out there at your local library that will tell you much more than I can about them!!