When you say lever, I'm going to assume you mean a dropweight machine.Dropweights are some of the simplest machines to use that provide consistent string tension. While in general, electronic constant pull machines are the best, dropweights can still produce a stringjob that is very close in performance provided you're experienced in using dropweights.
The pulling mechanism shouldn't be an issue. What you should be concerned with is to check the mounting system works properly for your racquet and holds the racquet firm without slippage during the pull, and the clamps are in good working order.
Racquet shifting during tensioning or not mounted properly are some main causes for racquet head damage. Bad or worn clamps can damage the string or loss of tension after each pull.