tStringList(Delphi) vs. tStringCollection (Borland Pascal 7), Speed

With Borland  Pascal 7.0 we've been working extensively with
tStringCollections to read strings from text files and working on with
the sorted lines in the StringCollections.
Trying to do the same with DELPHI's tStringList.ReadFromFile took about
5x the time used with the old StringCollections. Even working with the
'native' tList class didn't improve the result.
(FileSize: 350 kb, tStringCollection: 1,2s, tStringList: 6,2 s)
A striking fact is the rapidly growing swap file size (can be heard
acustically!) which is absolutely stable while filling a Borland Pascal
7.0 StringCollection.
The same phenomenon appears with DELPHI2;

Assuming that tStringList is the replacing class for tStringCollection
objects, we're asking for explanation and help to solve this problem.