The single best application of IMR 800-X in handgun cartridges is the the 10mm. Particularly reloaders that are weighing each individual powder charge. 800-X was originally introduced for magnum shotgun loads. It has a very large flake size. The largest I know of.
If you were to weigh the charges you are throwing with the .5cc dipper I think you would find a noticeable variation in charge weights. 800-X does not meter well using most powders measures. For this reason along with its slower burn rate, I would not use it for .38 Special.
Extruded flake powders get a lot of recommendation for .38 Special, particularly Unique. I started handloading with an extruded flake powder and that was Blue Dot in the .41 Magnum. It was many years before I discovered the virtue of ball (spherical) powders. Now, they are all I use for loading handgun cartridges. They meter much better than extruded flake and there are so many good ball powders that you can find a good one for any handgun application. In particular, W231 is used for many such applications and it is frequently used for .38 Special. The only fault that I have with it is that it burns somewhat dirty. No problem because there is one even better that is nearly identical to W231 and burns cleaner. That would be Ramshot ZIP. It also gives a bit better performance in most handgun cartridges.
Regardless of which powder you use you will find better uniformity of charge weights, whether thrown with a powder measure or dippers, when using ball (spherical) powder. If you want a higher perfomance powder than ZIP, Ramshot also makes a powder called Silhouette and there is good data for .38 Special. If I were out to make high perfromance defense loads for .38 Special and +P is what I'm talking about, I would use Silhouette because it also has a flash inhibitor so you don't get a giant fireball when you shoot your loads at night. Vihta Vouri also has several ball (spherical) powders like N340, 3N37, N350 that will work well but they are considerably more expensive than Silhouette and ZIP. Silhouette also works extremely well in 9mm and .40 S&W loads should you ever decide to start loading those.
You can find data for ZIP and Silhouette at
www.ramshot.com