There are many ways of performing a blepharoplasty, there are indications for each of them, but most important it is the experience of your surgeon. The traditional teaching is that with a external approach you will have more chances of ectropion ( pulling of your lid), you can have also problems with the transconjunctival approach, in my opinion the most important factor its the experience of your surgeon. With the external approach the surgeon should be able to improve certain problems, which are very difficult to fix with the internal approach, specially the eyelid/cheek junction line. Check pictures of the surgeons you visit, specially the lateral view.
Good luck