Which is the more invasive and uncomfortable of the 2 dental procedures if there ever were a choice of either: internal or external sinus lift?

sinus lift: By internal do you mean accessing the sinus laterally and lifting the entire sinus membrane;external=lifting the membrane when the implant is placed and only in that area of the sinus then the latter is much more comfortable and less invasive.

Depends on you...: The external sinus lift is probably more invasive, but the reality is that bone anatomy is individual to you and it could go either way depending on other anatomy, existing dental work and treatment sequencing for subsequent restorations. This would be a great conversation for you to have with your oral surgeon or periodontist.

Internal vs external: Assuming the procedure is necessary to augment the bone in preparation for an implant, an internal sinus lift (or sinus bump)is usually less invasive and healing is relatively easy. However, when more bone is needed, an external sinus lift is on order. Follow the recommendation of the surgeon, since it really depends on the situation and amount of bone needed. Both procedures are quite tolerable!

External : In most cases internal sinus left is the standard in prep. For implants. In more compacted cases where more bone is needed external technique might be used. Both are very tolerable providing following post operative instructions and care.

Internal: An external sinus lift is considered to be the more invasive of the two procedures. It is a larger incision. Both are effective ways of increasing bone volume for the placement of implants. Pain is very subjective to an individual and is difficult to predict but it can be managed and minimized by your surgeon. I would chose the internal sinus bump if it met your restorative goals.

Lateral = + invasive: Your upper back teeth have a hollow sinus above them. If an implant were place in that area it would be like punching through dry wall. A sinus lift of granular bone (placed laterally from the side, or crestal from the top (chased up with an implant) acts as a back stop between the boney roof of your mouth and the rubber balloon sinus membrane. Lateral lifts for multi teeth, crestal for singles.