I've owned two Mi4LP's for 2+ years, and I owned a TC6.1 for about 4 months.
The TC6.1 didn't go together quite as clean as the Mi4LPs, but it did go together and drive well. The reason I sold it is because it wasn't working any better for me than the Mi4LP, and there was more demand and I could get more for it, and hadn't invested much in parts.
Things the TC6.1 offers over the Mi4 line:
- Easy roll center adjustment out of the box. This is an expensive, heavy, PITA option on the Mi4 series.
- Cheap parts that your LHS probably stocks
- Tons of setup advice
- Lighter weight than the Mi4LP, not sure if it's lighter than a CX or CXL.
- Awesome gear diff
- Better battery retention with forward/backward option (the CXL offers two battery positions)
- Better servo mounting
- Way, way more aftermarket support.
The TC6.1 was strong and drove well. The only thing I broke was 1 C-Hub, and only after a lot of gnarly crashing.
Things that didn't impress me with the TC6.1:
- Shocks: I like the screw-retained piston, but that's it. They're black which makes it really hard to see bubbles. I couldn't get them to seal consistently. The RSD bladders are a borderline required option. The upper spring seats are too loose. And I couldn't get even stiction between all 4 shocks, and never figured out why.
- Springs: Inconsistent length. HPI and Spec-R don't fit the retainers well. RSD are nice, but you have to pay more.
- Screws: the m3x5 countersunk kit screws are crap, but ProTek replacements are pretty cheap.
Things the Mi4CX line offers over the TC6.1:
- Great build quality
- Motor mount clamp for left/right balance
- Much nicer shocks. Think TRF quality.
Things that don't impress me with the Mi4 line:
- Springs: Inconsistent length. Aftermarket ones fit well, though.
- Weight: It can be challenging to get the LP down to 1380, but I think the CX and CXL are better in that respect.
- Lack of setup help. Nobody runs 'em in my area. Although Hofer's geometry does seem to work.
If you're really interested in Schumacher, I'd highly recommended looking at the CXL from www.stormerhobbies.com
. It's enough improved over the CX to justify the extra $120 over amain's price on the CX.
If I were starting from scratch, though, I'd probably go with the TC6.1, especially if you can find a used one at a good price. The reasons being kit price, parts prices and availability, setup help, weight, and aftermarket support.