On the surface, Weil and Geil have little in common as far as German producers go. Robert Weil is probably second to only Egon Muller among German producers in terms of the prices they charge, which is why I have bought and tried very few of their wines thus far (especially when Leitz' wines cost much less). That being said, the quality of their wines is quite high, and they are considered by many to be the best in the Rheingau.
Geil, on the other hand, is an up-and-coming Rheinhessen producer who charges very reasonable prices. The Geil Riesling cost less than half of what the Weil retails for. Additionally, Geil makes some good QPR Scheurebe and Muskateller; I have also heard very positive things about their Silvaner, but have yet to find it. Although Geil may not be any threat to Keller in terms of Rheinhessen greatness, they still deserve recognition as perhaps the best value producer in their region.
2011 Oekonomierat Johann Geil I. Erben Bechtheimer Riesling Spätlese “S”
From Bechtheimer Geyersberg, though only the name of the village is on the label. Chalky/mineral nose. Full, ripe, round, off-dry, with moderate glycerin/acidity; tastes of tropical fruits, apricots, and citrus fruits, with floral/mineral notes. Very good. I also really like the new blue labels that Geil has inaugurated with this vintage.
2008 Robert Weil* Kiedricher Turmberg Riesling Trocken
Rather mineral, citrusy, slightly earthy/spicy nose. Medium to full-bodied, round, ripe, bone dry; fruitier than many Trockens, in an elegant, compact style. Although there is a crisp, mineral edge here, the geology takes a backseat to the fruit here. Full of apricot, pink grapefruit, and watermelon flavors, with floral notes, becoming more citrusy on the finish. No comment on the label here, except that Weil is an example of why you should buy based on the inside, rather than the outside of the bottle.
* One criticism that I have read of Robert Weil in the past is their supposed reliance on cultured yeasts. Now, I see that the website for Loosen Bros. (Weil’s current importer) mentions that at least all of the top dry wines are made with native yeasts. Presumably, by implication, at least the estate Rieslings are still being made with cultured yeasts. I don't know about their single-vineyard QmP Rieslings, but would be quite surprised if any of their top wines from the Gräfenberg used any manufactured yeasts in this day.