Which would you recommend; drain or drainless Tummy tuck?

In my opinion, there are no cons.  Other than adding some time, and therefore some expense to the procedure, there is no downside or risk to using a drainless technique.  The flap has to be sutured down evenly without dimpling the skin, and the space needs to be closed thoroughly. When this is done correctly, the patient is free from all  the cons associated with drains, namely scarring from drain holes, discomfort and limited mobility from drains, reoccurrence of fluid collection when drains are removed, and a relatively high percentage, 5-24% in the literature of having to aspirate fluid collections multiple times, and the risk of a persistent fluid collection or bursa that will require another operation to correct. Drainless tummy  tucks are an integral part of my procedure.   A meta-analysis in the Aesthetic Surgery Journal, 

Aesthet Surg J. 2017 Mar 1;37(3):316-323. doi: 10.1093/asj/sjw192.

Seretis K, Goulis, D, Demiri EC, Lykoudis, EG

Prevention of Seroma Formation Following Abdominoplasty: A Systematic Review and Meta-Analysis

reviewed all the literature on this topic, and found that "preventive measures" decreased the incidence of seroma four-fold. One of the studies included in the "preventive group" that used only progressive tension sutures, from 2006, showed fluid accumulation between the sutures, detected only on ultrasound. This fluid was not clinically detectable by palpation or inspection and resulted in no need for seroma aspiration or any complication. The total amount of fluid associated with clinical complications including drainage in the other groups was greater than 80 cc, and the total amount of non-clinically detectable fluid in the progressive-tension group was always 80 cc or less. The use of drains plus progressive tension sutures did not change the amount of fluid, so there is really no benefit to using drains plus progressive tension sutures.

The study was discussed by Pollock and Pollock, who noted that in their series of 565 patients using progressive tension sutures they never had a clinically significant seroma. When a seroma occurs, it may require multiple visits and aspirations, and if persistent, introduction of antibiotic sclerosing solutions, or reoperation to remove a fluid filled fibrous cavity. The drain opening may leave a scar in the incision or pubic mons which may become pigmented or depressed. Not having to use drains spares the patient and plastic surgeon from the chance of these undesirable events and/or outcomes.

My experience mirrors that of Drs. Pollack.  I have had no clinically significant seromas while using progressive tension sutures in the past five years or so.
Rather than use the 15-20 individually-placed sutures described by Drs. Pollock, I completely close the dead space with continuous PDO and monoderm Quill sutures. These sutures effectively reduce the dead space to almost nothing, so even the small amount of fluid that might collect between the sutures, cannot create any significant seroma. Using running Quill sutures allows relatively rapid dead space closure as no knot-tying is needed. The umbilical location is confirmed with a Lockwood flap marker before the lower abdominal closure is completed.

Our meta-analysis research (link below) showed that "drainless tummy tuck (abdominoplasty) with progressive tension sutures" were more effective than tummy tuck with drains in reducing seroma (fluid buildup) and reoperation rates, with no difference for hematomas or infections. The potential con is contour deformity and dimpling if the sutures are not placed correctly by an experienced surgeon.
Many plastic surgeons continue to use drains during tummy tucks because it has been the standard practice for many years. Drains are traditionally used to prevent fluid accumulation under the skin, a common occurrence after the procedure. The accumulation of fluid, known as a seroma, can slow healing and lead to complications. Using drains helps remove this fluid, ensuring proper healing and minimizing the risk of complications. However, drains can be uncomfortable, require additional care, and increase the risk of infection at the insertion points. They can also leave scars, even after they are removed.
The advent of the "drainless" tummy tuck, typically achieved through the use of progressive tension sutures, offers an alternative to this approach. These sutures help to close any dead space in the skin flap, significantly reducing the likelihood of fluid buildup and seromas. This technique not only eliminates the need for drains but can also result in faster recovery times and less post-operative discomfort for patients. While it has been shown to be highly effective, it is not without its challenges, such as a slightly longer surgical time and the need for a highly skilled surgeon to perform the procedure. Some surgeons may still prefer to use drains out of familiarity or due to concerns about fluid accumulation, especially in patients with certain body types or those undergoing significant liposuction. However, as more evidence supporting the benefits of drainless tummy tucks accumulates, this method is becoming increasingly popular for its enhanced patient comfort and streamlined recovery process.
While not every patient is a suitable candidate for a drainless approach, the procedure has proven to be a highly effective option. Your plastic surgeon needs experience in this technique, because incorrect placement of the sutures can cause major problems including contour deformities and possible need for re-operation. Be sure to consult with an experienced plastic surgeon to determine if a drainless tummy tuck is right for you!
Krishna Vyas, MD, PhD, MHSHarvard, Hopkins, & Mayo Clinic Trained Aesthetic Plastic SurgeonNew York, New York

Your choice of surgeon is far more important than choosing a surgeon based on the drain.  However, the drainless technique is very safe and will improve your experience and help you recover quicker.