Well, assuming all of your modelling assumptions are fulfilled, the modelling techniques do not differ and also assuming $R^2$ is the only model characteristic that differs between the models, I would consider a Student’s t-test (assumptions permitting) or Wilcoxon-Mann-Whitney test on the $R^2$s. In any case I would try to get a larger sample (costs permitting).

You can read more about different model selection measures, particularly AIC, [here](https://stats.stackexchange.com/questions/9171/aic-or-p-value-which-one-to-choose-for-model-selection).

If different modelling techniques were used you may find [this](https://stats.stackexchange.com/questions/22902/model-evaluation-and-comparison-for-selecting-the-best-model) interesting.