Here are some suggestions, some ideas from Mike Mraz's appearance on The Sunday Session 06-08-08 Non-Traditional Yeast and some are just my 2 cents.
1. Stick with a single hop variety with a rather neutral flavor and aroma. I'm thinking something along the lines of a noble hop. Use it only for bittering so you have an easier time picking up any ester aromas your yeast produces. Avoid dry hopping, cask conditioning, etc...
2. Avoid your caramel, dark, chocolate, black, etc... malts.
2. Mike Mraz compared a few Brett strains using a basic Belgian Golden Strong recipe, that started around 1.064 and finished at 1.007 (7.5% abv). He was able to do (2) 20 gallon batches and then split that into separate 5 gallon fermenters with different yeasts. He recommended brewing something with little residual sugar.
3. If you decide to use the same yeast strain, you can compare the outcome of the yeast by changing variables like, cold vs. warm fermentation temp, pitching at a higher temp/vs lower temp, high/low pitch rate, re-pitching yeast for bottle conditioning vs. using priming sugar, cold conditioning vs. bottling right after primary fermentation is done, open fermentation vs. closed, adding yeast nutrients vs. no nutrients. There are plenty of other things you can try, you get the idea.
4. Compare yeasts from different regions. English, Scottish, Irish, Belgian, French, German, American, Czech, Denmark, etc...
5. Compare different styles, Ales, Lagers, Lambics, Red Wine Yeasts, White Wine Yeasts, etc...
6. Ferment lager yeasts at ale temps and vice versa.