If you compare price between Keisei Skyliner and the NEX + SUICA combination offer, the difference is really minimal.

(NEX + SUICA offer is here:
http://www.jreast.co.jp/e/suica-nex/index.html)

Since the OP is headed to the Conrad, I think that the NEX is marginally ore convenient. But the Keisei Skyliner also works well. If I were the OP, I would just take whichever is leaving first.

(1) If OP takes the Keisei Skyliner, he can change to Yamanote Line at Nippori. (Take Yamanote line to Shinbashi - and walk 10 mins to Conrad)

(2) if OP takes the NEX, he can take a Sobu/Yokosuka Line train from the same platform that he arrives on. (Take Sobu/Yokosuka line to Shinbashi - and walk 10 mins to Conrad)

(3) If OP wants to avoid walking 10 mins to Conrad he should take N'EX to Tokyo and taxi to Conrad.