Lenovo’s ThinkPad SL400 tops the chart with power and flexibility while costing under $1300. Meanwhile, HP gives Lenovo a run for its money with the HP Compaq 6530b. Without the power brick, the HP is lighter than the Lenovo (5.3 pounds versus the SL400’s 6.1 pounds); it’s cheaper, too ($1195 versus $1295). Both work well ...