White D1 is much better because Black must reply at E1 (the approach-move ko at A1 against Black (White takes first) is very unfavorable ).The choice A1 or D1 is thus not about an endgame at E1 but about sente. With D1 White gets sente, because either player refrains now from starting an unfavorable ko against him/herself at A1, response at A2. Either player can resolve with A2, response A1 in gote for seki.