banjobj,
I am the PROUD owner of a Mighty TC18 (18.5 hp) with hydro 4x4, I've had it for about 1 1/2 years now and really like it...the ONLY thing that I would do differently if I could go back and do it again would be to get power steering, I didn't want to wait to order one and mine without power steering was in stock. I generally don't even notice no power steering except when I get in rough terrain, and if I ever add a FEL I will definitely notice it then.
If you look in the New Holland brochure, it shows what implements each of the TC tractors will handle and the only thing that is listed for a TC21 that is not listed for the TC18 is the 60" rear finishing mower...guess what I've been mowing with for the last two summers? Yep, a 60" Woods rear discharge 3 pt. finish mower, and with no problems, I do have to have the required weights on front and so would the TC21.
Other differences: TC18/21 have conventional glow plugs and 21D has Quick heat glow plugs, 18/21 have partial engine shielding and 21D has full, 18/21 have 4.0 gpm hydraulic pump 21D has 4.9, 18/21 have 20 amp alternator 21D has 35 amp, 18/21 have basic seat 21D has deluxe. You can see that you get more than just 2 1/2 hp when you jump up to the TC21D.
More pump flow would probably help that FEL, as far as what someone said about more headlights on the 21D, my TC18 lights up everything at night...it's got great lights. Weight is about 100 lbs. more on the TC21D and frame is the same size. Height of the 21D is 1" taller and rear tire width is about 1 1/2" more. Turning radius is tighter on the TC18 by 73.6" vs 81.5"
The TC18 handles a 4' rotary cutter like a champ too!
If you already had all of this info, sorry for the redundancy, but sometimes it helps to hear how someone else says it. /w3tcompact/icons/smile.gif
Good Luck, let me know when I can welcome you to "Club Blue"
JimBinMI