The Ehle's are popular around here for good reason(s), largely: quality and price. I would say that yes, the 100ml Ehle would be better (in terms of quality, I think it would be objectively better with regards to glass quality, quality of joints, workmanship in general etc.). The Ehle's are well-built for the price, not the thickest glass around but at under $100 that's hard to beat. Other options include HVY, SSFG, RXI, etc. Looking for straight tubes puts you in a buyer's market IME.
You could buy a diffused downstem if you're after a less chuggy, "smoother" hit...its more than worth it IMO. The benefit is not only diffusion (a buzzword which always seem to get people's heartbeats racing) but an easier pull. The Ehle diffused downstems allow you to displace air (vapor) easier than the stock downstem, the reasons for this are pretty clear.
Size is obviously a preferential thing but I think you'd be more than happy with that size; that is, I don't think it would be too big (FWIW, I use my PD with a few pieces that clock in considerably larger than the 100ml Ehle). If the price isn't an issue, the Ehle over the Black Leaf would be a no-brainer for me. That said, if price isn't an issue at all, its onwards and upwards!
(Some praise to the mods for merging these threads, makes sense IMO.)