DDX and Kodak Tmax Developer have similar properties to each other. They're not identical in properties to Xtol, but they're my usual recommendation for a great liquid developer. They are the best pushing developers I have tried. Tonality is great with most films. Grain is fine but not as fine as Xtol.
They are fairly expensive when used at their standard 1+4 dilutions, but they perform beautifully diluted 1+7. Multiply the standard developing times by 1.5 to get the times for the 1+7 dilutions.
DDX and Tmax Developer are especially beautiful with Ilford Delta and Kodak Tmax films, but work well with other films like Tri-X and HP5.