Switch your simulator server class
Linden Lab's land team is offering switcheroos on Second Life simulator server classes starting from Friday, 1 February and running until - well, I suppose until they change their minds.
The new deals allow you to either upgrade one non-mainland simulator from class 4 (those with lower class hardware - are there any? We don't think so - need not apply) or two swap two simulators where one is class 4 and the other is class 5.
Upgrading from class 4 to class 5 will jump your monthly fees for the sim to US$295/month (the standard class 5 fee) with no additional upgrade cost.
The switcheroo option costs US$100 and allows you to switch two of your sims, though they have to be owned by the same account, but since you still have the same number of class 4 and class 5 simulators at the end, the monthly fees remain unchanged.
None of this applies to mainland simulators, of course, whose server hardware is allocated by Linden Lab, as they see fit.
Class 5 hardware is generally considered to be more capable than class 4 hardware, though there are no clear independent metrics. The available information on class 4 vs class 5 simulator performance is largely anecdotal, and not easily measured.
