The Marshall IQP

The August Chess Life had an interesting article by GM Andy Soltis, 'The Marshall Variations of the Sicilian and French Defenses'. Soltis' articles are always interesting, but this was about two similar variations that I had bever seen before.

The diagram shows the position after 1.e4 c5 2.Nf3 e6 3.d4 d5. This is ECO B40.01, which Soltis calls 'The Marshall Variation of the Sicilian'. ECO also attributes 3...d5 to Frank Marshall.

'The Marshall Variation of the French' is 1.e4 e6 2.d4 d5 3.Nc3 c5, ECO C10.01. The authoritative ECO agrees again that the third move is Marshall's. The position is similar to the digram, except a Knight has been developed to c3 instead of f3.

My old copies of ECO only give a few lines in each variation, all of them ending with advantage to White (plus over minus). The problem is that Black ends up with an isolated d-Pawn. This leads to the question: If the IQP is playable in the French Tarrasch (3.Nd2 c5), why isn't it playable here?

Both variations should be worth a try in non-serious games.