I understand your desire to base your decision on A/B test results from other sites. It is sensible to want to base your decision on data, and it's hard to A/B test something like pricing. That said, I think you shouldn't do so -- A/B test results are highly dependent on the target audience, and different sites have different target audiences so...
You might want to read Ash Maurya's findings on SaaS plan structures (a bit down in the post). Key takeaway: in some markets simplicity is the most important feature.
Regarding the names, I personally feel that non-descriptive or non-evocative names like "Bronze / Silver / Gold" or "SME / Enterprise" are poor choices. I don't have data to back this up, it's just a feeling. I would prefer slightly more evocative names like "Student & Startup Edition" versus "Professional Edition". On the other hand, the names should not be so evocative that they steal all the attention.
Back to my first paragraph about target market -- I don't think you should use "Bronze / Silver / etc". Since you didn't say which market you're in and who your target audience is, I think that's the best I can say.
I personally don't like plan names with cheap metal names in them. Bronze feels cheap and if its a plan for my needs, I'm having second thoughts about subscribing to "Bronze"...
Also, I don't like plan names that are "non-standard"... as if there is not enough stuff I need to remember and know about as it is... reading someone else's Sprinkle vs. Rainy vs. Downpour, etc. plans is cute... but I prefer to associate the names with something familiar: Basic, Extended, Enterprise, etc... Maybe I'm just plain boring kinda guy :)
If you're targetting consumers and you have a "fun" product, perhaps catchy names would be great.. otherwise, IMHO, if you're going for B2B, I'd stick with "Basic/Premium/etc"
How many do you need? People don't recommend more then 3-4 anyway.
We struggled with this one ourselves at HubSpot.
In the end, we decided to go with the simplest thing we could come up with: Small, Medium, Large. Not sure if that was right or not, but it was in line with our "don't complicate things" philosophy.
Be careful about A/B tests for this... this is your product. You have a potential for confusing your customers when the "Gold" package they have been thinking about suddenly becomes "Professional".
I think that Bronze/Silver/Gold/Platinum schemes work when all editions have similar features but vary by level of support or a similar theme. Maybe bronze is next day response and 8-4, Gold is 24x7 with a 2 hour response and platinum adds something else that costs alot and is high margin.
The Basic/Professional/Enterprise type nomenclature is a great way to up-sell. Nobody wants to be basic.
I'm in favor of doing original names - IF they fit the motif of the product.
For example, my company (Textaurant ), is using "Appetizer," "Entree," and "Prix Fixe" - all restaurant-related terms which go well with the fact that we sell a service to restaurants. "Gold" and "Silver" might work just as well, but we want to show our fun side a bit.
Just don't go overboard, or get too silly.
Depending on the target market I would adjust the names accordingly, ie bronze/silver/gold for B2C and Basic/Pro/Enterprise for B2B. Overall I don't believe someone would not purchase because of plan name. As an example UserVoice uses metal plan names while GetSatisfaction uses more unique plan names. The services are similar as is their pricing, I wouldn't pick one over the other based on plan name but rather the value of the services provided.
Perhaps try a service like Optimizely which makes A/B testing very easy and see what happens.