Good choice , Go for Yamaha SZ-X, can't say much about D150, anytime Bajaj may sack(*) it and the re-sale may plummet.
(*) Rajiv Bajaj himself has said some models will be discontinued after 'new' bikes are introduced, can't say whether D150 will be alive in the new list.

Go for SZ-X bro it has good mileage with a performance of FZ...

@Wanted_DoA and Vipin: Guys check your language.

everybody must respect other's views and not use offensive language.

i had some doubts regarding vipin's opinion, so raised questions.

@ Vipin: I had asked my doubts in a very peaceful way, and respect the same from others.

Mods plz take a note of this.

You can safely choose D150.. considering that you are going to use it for only 2 years. As far as I know.. reported mileage figures of D150 are better than that of SZ-X/R.. and all the options given in SZ-R or standard on D150.. and you save almost 10k, you get better performance as well.
You may not experience the same smoothness you get in SZ series.. but 10K is a very good trade-off for a noticeable drop in smoothness. If I were you, I would go straight for D150.

Another option is to buy a used bike.. Unicorn/Shine, you get good ones at around 40k.. and they are perceived to be good value holders.. so you won't loose too much while selling. If it's a new bike.. you may end up selling it for atleast 20k less than what you bought it for!!