Both of the reactions are correct. However, the second reaction is written by 'adding' two reaction equations.
When nitrogen dioxide($\ce{NO2}$) is dissolved in water, it produces a 1:1 mixture of nitric acid($\ce{HNO3)}$ and nitrous acid(HNO2). $$\ce{2NO2(g) +H2O(l)->HNO3(aq) +HNO2(aq)}$$
i.e.$$\ce{2NO2(g) +2H2O(l)->H3O+(aq) +NO3-(aq) + HNO2(aq)}$$
However, since nitrous acid is unstable in any environment except very cold solution, it decomposes slowly into $\ce{NO}$ and $\ce{HNO3}$:
$$\ce{3HNO2(aq)->2NO(g) +H3O+(aq) + NO3-(aq)}$$
Your second reaction equation is obtained by adding these two reaction together.
Reference:
- Housecroft, C. E.; Constable, E. C. Chemistry, 4th ed.; Pearson, 2010, p 777.
Note:
I wrote the $\ce{H+}$ ions as $\ce{H3O+}$, so there is an extra water molecule on the left side of the equation, in each case.