I don't think Tether can be used as an investment, because you can't get profit from investing in Tether, then if you want to try your luck, so you can invest in XRP, because the price of XRP haven't increased very high in 2021 and haven't even reached its ATH price, therefore I believe if there is another bull run, then of course the price of XRP will most likely increase very high and can reach its ATH price, because people already believe to investing in XRP again and now is still the right time to invest in XRP, because the price of XRP is still cheap.
I think at this current situation it still a little bit risky to put our money into XRP because XRP still has a problem with SEC and it still not done. So i think we better stick with big coins who don't have any problem with government or SEC which is ethereum is the best choice to invest.