My first post here <img src="/images/graemlins/smile.gif" alt="" />

Short presentation: Scandinanvian MD with some ER practice and who recently did the (American) AdvancedTraumaLifeSupport course (the most used and probably best course in this field for MDs and Surgeons currently available)

Over to your questions:

1. If practically possible the absolutely best way to stop bleeding is manual pressure. Just look in the wound where the bleeding comes from and press there just hard enough to make it stop. This way no further harm is caused and the bleeding is stopped. Tie-off and suture damages tissue and complicates definitive surgery later on.
Suture is the most efficient of these two alternatives in some cases but also more technically difficult and might cause more damage.

2. Not sure I understand your question correctly. In the field the only wounds I would suture are scalp wounds without cranial fractures, if it bleeds profusely and the bleeding cannot be stopped in any other way. The suture in this case is a very efficient way of stopping the bleeding and infections are not as dangerous as in other parts of the body.
If a patient arrives to the hospital with a wound closed in the field I would suture it after rigorous flushing with saline if:
* The wound is caused by a clean object.
* It is no more than 8 hours old.
* Pulse,skin temperature, sensitivity and motor function "below" the wound all are ok. (Otherwise surgery might be required.)

The above answers are based on my personal competence and experience and might differ from what is the best solutions for other people in other places.