DataContext LINQ Queries - Should I use my own data object classes? - performance

Question

I apologize if my vocabulary is off on the following question.
I have an SQL Database that has multiple relationships to tables within that database. I've created a DataContext for this database and create a repository of functions used to call it's data.
My question is, because of the relationships (Multiple Linked tables).
Should I create my own class object to hold the results and only grab the needed table's column data like the following:
public IQueryable<VM_userLogs> getUserLogsVM(Nullable<DateTime> startDate, Nullable<DateTime> endDate)
{
if (startDate == null) {
startDate = Convert.ToDateTime("01-01-1900");
}
if (endDate == null) {
endDate = Convert.ToDateTime("01-01-2900");
}
IQueryable<VM_userLogs> logs = from l in ctx.tools_trt_userLogs
where l.timeStamp >= startDate & l.timeStamp <= endDate
select new VM_userLogs {
LOG_ID = l.logId,
NTLOGIN = l.ntLogin,
PRODUCT = l.productName,
SEGMENT = l.segmentName,
PRIORITY = l.priority,
GROUP = l.groupName,
ANSWER = l.answerText,
TIMESTAMP = l.timeStamp,
URL = l.url
};
return logs;
}
or can I just call the underlying object from the datacontext and NOT take a big performance hit... Like the following:
public IQueryable<tools_trt_userLogs> getUserLogs(Nullable<DateTime> startDate, Nullable<DateTime> endDate)
{
if (startDate == null)
{
startDate = Convert.ToDateTime("01-01-1900");
}
if (endDate == null)
{
endDate = Convert.ToDateTime("01-01-2900");
}
IQueryable<tools_trt_userLogs> logs = from l in ctx.tools_trt_userLogs
where l.timeStamp >= startDate & l.timeStamp <= endDate
select l;
return logs;
}