I finally went to the other place - Lazzat-e-Lucknow. It is now no longer on my list of must-tries. I have - it may be officially stated - tried it.
I tried, in particular the gilawati (in both kabab and roll versions), the seekh (in the roll version, though I did extract and eat some of the kabab by itself too) and the mutton biriyani. The first thing to notice is that the menu is a lot smaller than Dhuan, no arabic pretensions here but some Punjabi has nevertheless crept in. A single laminated tablemat-size sheet with dogeared edges suffices for the menu. Seating is pleasant, and there's even an AC section for those who can climb the short but steep stairs that characterize Versova's mezanines.
Enough of the ambience - here's my view of the food. They don't have kakori. Gilawatis were great, and in particular the paratha (ulta-tawa lucknow style, the menu insisted) that made up the roll was very nice; thin, beautifully non-greasy and quite edible all on its own. I particularly recommend the gilawati roll - all those soft bursting kababs releasing flavour, ecstasy and mmmm sounds, etc etc; I thought the seekh roll had a poor meat-paratha ratio though my sneaked out piece of seekh was, by itself, quite nice. Mutton Biriyani was the dry kinds, not the usual Mumbai curry rice disguised under a nice name, but was about average. The mutton pieces were good (all nalli too) but the rice part was not going to drive Kolkata's Shiraj out of business. No potato too.
Verdict: Great gilawati (slightly better methinks, than Dhuan, though not quite Kakori House). Ok biriyani (better than most other places, but not great in absolute terms). Excellent parathas. Promising seekh. Totally VFM prices.