I have both cameras - they are the basis of my film photography kit.
My SRT-102 is a rock-solid example of what was going on in the camera world in the 60-70s. It is heavy and very well built. I have had it CLAd a couple of times over its long lifespan. It works flawlessly and its meter is very accurate, within the EV range of a CdS-type photocell. I use a C.R.I.S. battery adapter with a silver-oxide cell. I tend to use the SRT with larger lenses and with the MC Rokkor-X 100mm macro lens, usually with a tripod. The MLU feature is nice when doing macrophotography. There are a lot of resources for having the camera repaired or adjusted, and service is usually quite reasonable. Lots of spare parts are available as Minolta made a lot of SRTs - plenty of carcasses to scavenge from.
The XD-11 is an absolute jewel. To me, it exemplifies the height of progression of MF 35mm film cameras. It feels great in the hand, all the controls are right where they should be, it is light for an all-metal camera and has a very good silicon photocell. The acute-matte viewfinder is terrific. It uses a modern lithium battery. I use it for 90% of my film photography. It is an electronic camera for the most part, and the electronics are getting old. I have never had any mechanical or electrical problems with my XD-11, but the potential, I suppose, is there, and there aren't nearly as many resources for getting the camera repaired as there are for the SRTs. Parts are scarce.
Both cameras get you into the great Rokkor lenses but to use all the features of the XD the later MD lenses work best. I have noticed that prices are climbing for Minolta glass recently, probably because they can be used on digital cameras with a Micro 4/3 sensor.
If this is your first foray into film cameras, I think the SRT-102 may be the best choice. It's a great fully manual camera, and the prices are pretty reasonable. It can be CLAd for under a hundred bucks and will likely outlast the average photographer! The XD-11 might be a camera to progress to at some point, but keep in mind that nice ones command fairly high prices. As another post mentioned - why not get both? I find that mine complement each other very well.