Dear Ahmed,

Based on my personal experience using pocl3 will lead to the same result.

Yes you can use POCl3 for the chlorination of pyrimidine in the presence of base.

Please see the below link for further information

http://www.mdpi.com/1420-3049/17/4/4533/htm

Both the conditions are permissible but in typical conditions the reaction needs PCl5 to promote the reaction.

POCl3 will give the same result

Most of the time results will be similar, although in some situations addition of PCl5 could be beneficial. If a particular procedure requires POCl3/PCl5 mixture, I will try to read the paper carefully to understand why it is used instead of just POCl3. Perhaps sometimes POCl3 is of poor quality, then adding PCl5 will certainly help.

http://onlinelibrary.wiley.com/doi/10.1002/jhet.5570210447/pdf

Check this publication